Research Intern Log at BoP Hub
Day 1 (5/6/2012 Tue)
Categorized the research materials by continents, subcontinents and general information.
Collected 39 pdf documents: reports, articles and publication from several websites.
Next Step: Mine UNEP and start reading on the general information.
Day 2 (6/6/2012 Wed)
Collected 21 more pdf files. There are now 60 pdf documents to read and research.
Started reading the pdf document "Design Principles for Wood Burning Stoves" (40 pages)
Basic schematics of Wood burning Cook stoves.
Efficiency can be broadly divided into Combustion efficiency and Heat Transfer efficiency
Optimizing both efficiencies, with Heat Transfer taking priority over Combustion Efficiency.
Day 3 (7/6/2012 Thur)
10 Design Principles for Wood Stoves.
Winarski, Baldwin and calculations for dimensions of wood-burning cook stove (revolves around the cross sectional area of the channel).
Materials for Combustion Chambers: ceramic (Thai Bucket Stove, Kenyan Jiko Stove)
Nueva Esperansa manufactures ceramic using clay, sand, tree gum and horse manure. Used in Justa and Eco Stoves.
Ceramic is a heavy dense material with high thermal mass - although it acts as the stove body, it needs to be insulated to prevent minimize its heat absorption.
Alternative material 1: Cheap Ceramic Floor Tile "Baldosa" that lasts 4 years.
Alternative material 2: Insulative Ceramic made from mixing clay with "fillers".
Fillers can be lightweight fireproof material (like Vermiculite, Pumice and Perlite) or organic materials (like sawdust and charcoal).
In-field WBT (Water Boiling Test): Beginning, High Power (Cold Start) Phase, High Power (Hot Start) Phase, Low Power (Simmering) Test, Analysis
Finished reading the pdf document "Design Principles for Wood Burning Stoves" (40 pages)
Day 4 (8/6/2012 Fri)
Started reading the pdf document "Ashden - Technology - Cook Stoves" (4 Pages)
Advanced stoves known as semi-gasifiers, separate the combustion of solid fuel and gases, each with its own air supply. The latest designs control air flow with a small fan, which improves combustion efficiency.
Improved Standing-up Stove (Wood based): Rocket Justa Stove by Trees Water People and AHDESA, ONIL Stove by HELPS, REC stove in Eritrea, Lower "Chula" style designed by Grameen Shakti in Bangladesh (very cheap because mud is used).
Improved Bucket Stoves (Charcoal Based): Kenyan Jiko Stove
GERES initially designed Lao Stove for Cambodians, but their "New Lao" (improved designs in collaboration with local artisans and stove users) uses slightly different dimensions to improve air flow; extra holes across the grate and tapered pot rests. Rice Husk and Ash are used as insulating materials for the stove bucket body.
Mass Produced Portable Rocket Stoves: StoveTec by Aprovecho
Biomass Briguette Stoves: Sawdust Stove by Kisangani Smith, Institutional Stove by Nishant, Sanju Chuhal Stove
Approximate Costs of the above mentioned Stoves in USD
Global Alliance for Clean Cook Stoves (GACC)
Millenium Development Goal of eradicating extreme poverty by 2015
Finished reading the pdf document "Ashden - Technology - Cook Stoves" (4 Pages)
Started reading the pdf document "Guide to Desigining Retained Heat Cookstoves" (16 Pages)
When boiling temperature has been reached, there is enough energy (heat from the stove) to simmer the food (keep it at or below boiling point). Additional energy only serves to convert water to steam without raising the temperature of the contents of the pot. This additional energy wastes scarce wood and water that might have been gathered over long distances.
Insulation materials keep the pot at a cooking temperature long enough to complete the cooking cycle.
Advantages of Using RHC: Free cook from tending fire to do other tasks, No further usage of fuel, Minimal water use, Pot contents will not boil dry or scorch, No emissions when using RHC, Portable
Practical benefits: Keep water heated overnight for fast preparation of breakfast, Preserve contents for later meal, Useful for preparing food that takes very long to cook.
In contrast with principles of Wood Stove, the RHC encourages use of pots with high thermal mass- it will absorb large amounts of heat, allowing it to continue to simmer in an insulated environment.
Outer Container: Used to hold insulation, Inner Container and pot. However the material of the outer pot makes little difference if the insulation is relatively weak. The Outer Container, in its most primitive form, is a hole in the ground that holds insulation in place. A tightly-woven basket can also be used. The Haybox is the most typical RHC used.
Insulation Materials: Hay, Straw, Leaves, Newspapers, Corn Shucks, Rice Husk, Corrugated Cardboard, Wool Blanket, Cotton, Styrofoam, Pumice, Perlite, Ash.
Inner Container: Tight fitting, Low Thermal Mass, Protects insulation from moisture.
Types of RHC Priojects: Household DIY, Village Construction, Mass Production in Factories and Distribution.
Design Process: Research, Conceptual Design, Prototype and Laboratory Testing, Field Testing, Design Review, Pilot Production, Hard Production
Marketing and Distribution: Product Introduction, Training and Support, Awareness Building (Radio, Village to Village, Local NGOs)
It is expected that initially the communities wil lbe skeptical of the RHC. There should be demonstrations rather than just a verbal pitch or data sheets. It will be even better to collaborate with a NGO that is already well known and trusted in the village.
Village cooks and community leaders should be engaged. If they endorse the RHC, it will gain widespread acceptance in the village.
Even the best designed RHC will yield poor results if procedures are not carried out properly. For example, the operator fails to transfer the pot immediately into the RHC or seal it properly.
Many recipes need to be modified for cooking in an RHC. Research on local recipes and training to incorporate new cooking techniques should be provided.
Finished reading the pdf document "Guide to Desigining Retained Heat Cookstoves" (16 Pages)
Started reading the powerpoint "Clean Cookstoves -Technology Poised for a Breakthrough" (17 Slides)
2010 Waxman-Markey Bill aims to reduce: fuel by 50%, black carbon by 60%, childhood pneumonia by 30%
According to Aprovecho Research Center, there are 5 types of Improved Cook Stoves (ICS):
Natural Draft Rocket Stoves, Fan Stoves (Top Loaded and Side Feed), Semi Gassifiers, Natural Draft (TLUD), Institutional Stove
Powerpoint lists the type of fuels used, as well as the % reduction in fuel used and emissions.
Stove community could support mass manufacturing/distribution.
Very clean Stoves can be sold at the local market price due to a $5 to $10 per year carbon credit
Finished reading the powerpoint "Clean Cookstoves -Technology Poised for a Breakthrough" (17 Slides)
Started reading the pdf document "Ashden - Technology - Biomass Briquettes and Pellets" (3 Pages)
Briquetting is a way to convert loose biomass residues, suchas sawdust, straw or rice husk, into high density solid blocksthat can be used as a fuel.
Two types of briquetting: High pressure briquetting and Low pressure briquetting
The best materials for high pressure briquetting are sawdust and other woody residues because they contain a high proportion of lignin.
In low pressure briquetting, the powdered biomass is mixed into a paste with a binder (eg. starch), clay and water. A briquetting press is used to push the paste into a mould or through an extruder, or it can simply be shaped by hand. The briquettes produced are left to dry, so that the binder sets and holds the biomass powder together.
ARTI developed a portable kiln to produce char from sugar-cane leaves that are usually burned in the fields, and a hand press to make the loose char into briquettes. Similar systems have been developed for use with coconut husks and nut shells.
Kampala Jellitone Suppliers (KJS) runs a biomass briquettingbusiness in Uganda.
In India, Nishant Bioenergy focuses on developing briquette stoves to give users an alternative to cooking on increasingly expensive LPG (Liquid Petroleum Gas).
In India, Abellon CleanEnergy produces pellets using both agricultural residues and sawdust. Most are used to replace lignite and coal in factory boilers.
Nottinghamshire County Council ran a programme to convert coal boilers in schools to run on pellets, and also install pellet-fuelled boilers to replace old coal boilers.
Briquetting is a way to make use of biomass residues that would otherwise go to waste.
It replaces the wood and charcoal (often produced unsustainably) and fossil fuels, cutting greenhouse gas emissions.
Briquettes are easier to store and use for cooking than wood because they are uniform in size and composition.
They are much cleaner to handle than charcoal or coal, and produce less local air pollution.
Pdf contains costs and trends in using briquettes.
Finished reading the pdf document "Ashden - Technology - Biomass Briquettes and Pellets" (3 Pages)
Day 5 (11/6/2012 Mon)
Started reading the pdf document "WFP and Safe Access to Firewood" (4 pages)
Problems associated with Firewood collection: Soil erosion, risk of attack and rape landmines, Resource war, indoor air pollution, Climate Change
UN/NGO Task Force on SafeAccess to Firewood and alternative Energy in Humanitarian Settings (SAFE).
Four-pronged strategy: Scale Up, Explore new Energy Technology, Alternative livelihood, Education
Positive results: Reduce violence against women, Creating alternative livelihoods for women, Support families sending children to school, Decrease indoor air pollution, reduce environmental degradation, Identify potential benefits from carbon credits, Introducing innovative and sustainable clean fuel technologies.
Alternative Livelihood: Making Briquettes, Stove Construction, Tree Planting, Rainwater Harvesting
Finished reading the pdf document "WFP and Safe Access to Firewood" (4 pages)
Started reading the pdf document "Environmental Health Perspectives - Better Breathing" (6 pages)
Most Indian families prepare their meals over a 3-stone open fire or Chulha (a traditional clay/brick stove).
For hours daily "women and their small children breathe in amounts of smoke equivalent to consuming two packs of cigarettes per day,” the World Health Organization (WHO) reported in the 2006 report Fuel for Life: Household Energy and Health.
Smoke from open fires and traditional stoves: 90% Carbon Monoxide (CO) and 10% is mix of volatile organic compounds, polyaromatic hydrocarbons, metals, and particulate matter including PM10 (which easily penetrates airways) and PM2.5 (the smaller fraction, which penetrates deep into the lungs).
According to Fuel for Life, 24-hour levels of PM10 in homes that use solid fuels routinely reach 300–3,000 μg/m3 and may spike to 10,000 μg/m3 during cooking. The WHO recommends no more than an annual mean of 20 μg/m3 and a 24-hour mean of 50 μg/m3 .
Globally, an estimated 49% of deaths attributable to household use of solid fuel are due to pneumonia in children under age 5.
In a meta-analysis of 24 studies in the May 2008 issue of the Bulletin of the World Health Organization, Bruce and colleagues reported that, despite “substantial” differences among the studies, “this analysis demonstrated sufficient consistency to conclude that risk of pneumonia in young children is increased by exposure to unprocessed solid fuels by a factor of 1.8.”
RESPIRE: The use of stoves with chimneys in Guatemala reduced CO levels in the kitchen by about 90% and children’s exposure by an average 50% over 48 hours, the researchers reported 17 June 2009 ahead of print in the Journal of Exposure Science & Environmental Epidemiology. However children are exposed to smoke when they go outside and when they go to other homes, so their individual CO exposure levels don’t match levels in their own kitchen.
Knowing the health effects of different concentrations of smoke will give international agencies and governments the data necessary to establish “clean cook stove” standards that manufacturers must reach to be accredited. This ensures that customers who purchase an accredited “clean cook stove” can expect certain improvements in fuel use and reductions in indoor air pollution levels.
Stove Manufacturers: Envirofit, StoveTec, First Energy, WorldStove, and HELPS International
People buy stoves more for aspirational reasons.
Consumers know the smoke irritates their eyes and makes them cough, but they don’t always comprehend the long-term impact of breathing high levels of smoke
Some families will keep more than one type of stove in their homes. Usage studies show that families cook at most about 70% of their meals on their improved cook stove, although most will report full usage all the time.
“You can’t drop a stove into a household and walk away." Rita Colwell
Finished reading the pdf document "Environmental Health Perspectives - Better Breathing" (6 pages)
Started reading the pdf document "Project Surya - Reduction of Air Pollution and Global Warming" (14 pages)
Project Surya will deploy inexpensive solar and other energy-efficient cookers in rural India and document their role in reducing emissions of carbon dioxide and soot. Carbon dioxide and elemental carbon (two by-products of fossil fuel combustion, biofuel cooking and biomass burning) contribute as much as 70% to the global warming.
About half of the world’s population, and 75% of households in India, use biofuels and biomass (including wood, charcoal, crop residues and dung) to prepare food and heat their homes. More than 70% of India’s population lives in rural areas. Cooking accounts for about 60% of the overall energy and 80% of the non-commercial energy used in rural India. More than 90% of the cooking is done with fire wood and bovine dung.
Solid fuel use accounts for 4.8% of Sub-Saharan Africa’s disease burden, 2.5% of the disease burden in China, and just under 1% of the disease burden in the poorer Latin American countries.
The objectives of Project Surya are three-fold, listed below in the order of their importance:
- To eliminate the detrimental health effects of indoor smoke;
- To reduce the negative effects of elemental carbon in ABCs on the summer monsoon rainfall, Himalyan glacier retreat and agriculture;
- To mitigate the global warming effects of CO2 and elemental carbon.
Surya's cooking strategy: On sunny days, use Solar Cookers. On cloudy days or at night, use Biogas Stove and other clean stoves.
Engaging village children to collect data: weight of bio-fuels used each day, duration of cooking, and the time of the smoldering fire, down time for the devices and the additional maintenance required for the new cookers.
Collaborating with the One Laptop per Child Initiative (www.laptop.org) to engage local children in tracking the energy use habits in the villages.
Impact on Local, Regional and Global Society
Finished reading the pdf document "Project Surya - Reduction of Air Pollution and Global Warming" (14 pages)
Started reading the pdf document "Cookstoves and Black Carbon - Senate Briefing" (14 pages)
Typical carbon savings from an improved cookstove about 0.5-2 tCO2-e/year
The Power of Carbon Credits:
- Financial transaction vs development aid – no reductions, no money
- Demands extensive monitoring per established protocols
- Transaction costs incentivize: large projects + continued use of stoves
Key Limitation of Carbon Credit: focus is on fuel use/efficiency, not emissions. By itself, carbon financing won’t get us to advanced, super-clean stoves.
Cookstoves represent a large, controllable part of the black carbon inventory
Finished reading the pdf document "Cookstoves and Black Carbon - Senate Briefing" (14 pages)
Started reading the pdf document "Laboratory comparison of the global warming impact of five major types of biomass cooking stove" (10 pages)
There are two main types of emissions: CO2 (Carbon Dioxide) and PIC (products of incomplete combustion). Charcoal burning emit less CO2, but releases more PICs. There is a tradeoff in this case.
PICs consist of Carbon Monoxide (90% as mentioned earlier) and 10% consisting of volatile organic compounds, polyaromatic hydrocarbons (eg. Methane), metals, and particulate matter (PM10 and PM2.5).
Sustainable vs non-sustainable harvesting of biomass
Most PICs are oxidized to CO2, but in the meantime they have greater global warming potential (GWP) than CO2. Indeed comparing carbon gases released into the atmosphere, the least damaging from a global warming standpoint is CO2; most PICs have a higher impact per carbon atom [Smith etal., 2000]
Emissions from biomass cooking stoves
In perfect combustion, emissions from burning fuel wouldbe only carbon dioxide and water
If biomass was completely combusted, and the fuel was harvested sustainably, cooking with biomass could be a carbon-neutral situation.
Emissions of carbon monoxide in traditional wood-burning stoves are frequently as much as 10-15 % of the CO2 emissions, and this figure is even higher for charcoal. Carbon monoxide has a GWP of 1.9 times that of carbon dioxide [IPCC,2007], and is a large contributor to the localized air pollutionin urban areas.
Averaged over 100 years, CH4 has a GWP 25 times the same mass of CO2. Methane has an atmospheric lifetime of about 12 years. Methane is a part of the Kyoto Accords and is considered one of the most important greenhouse gases resulting from biomass burning[IPCC, 2007]
Emissions of unburned hydrocarbons indicate incomplete combustion and the vapors can be harmful if inhaled. Overall, the 100-year GWP of the NMHCs is approximately12 times that of CO2, with climate-forcing occurring because of their contribution to ozone formation[Edwards and Smith, 2002].
Nitrous oxide has an atmospheric lifetime of 120 years and GWP of 298 over 100 years. N2O is also a part of the primary Kyoto Accords and one of the primary gases considered in inventories of biomass-burning [IPCC, 2007]
NOx is a broad term for thevarious nitrogen oxides (other than N2O) produced during combustion when combustion temperatures reach a high enough level to burn some of the nitrogen in the air. NOx is an ozone precursor and when dissolved in atmospheric moisture can result in acid rain. Oxides of nitrogen affect atmospheric chemistry in complex ways, including interactions with OH radicals and contributing to ozone chemistry. They are presently thought to be greenhouse-neutral overall [Bond, 2007], and as such the IPCC does not present a GWP for NOx [IPCC, 2007]
PM is composed of tiny solid or liquid particles. The effects of inhaling particulate matter have been widely studied in humans and animals. They include asthma, cardiovascular disease, and premature death. By weight, particles can have an extremely strong effect on the atmosphere by absorbing and/or scattering the sun’s incoming radiation. Different types of particles have varying levels of scattering vs. absorption, defined by their single scattering albedo (SSA). If the particles have low SSA, they absorb more sunlight and create more warming in the atmosphere. Generally, particles that have low SSA have a higher ratio of elemental to organic carbon in their composition. Though not a part of the Kyoto agreement, the climate-forcing effects of the particles emitted from biomass combustion are quite substantial.
Elemental or black carbon particles are carbon particles that will not volatilize at a temperature of ~600º C (in an inert environment). EC is produced in flaming fires and is also called soot. Soot is most commonly emitted from the burning of biomass,coal, and diesel fuel. It is one of the most important absorbingaerosol species in the atmosphere. Elemental carbonfrom combustion has a GWP 680 times that of CO2 [Roden and Bond, 2006; Bond and Sun, 2005].
Elemental Carbon = Soot = Black Carbon
Organic carbon (OC) and organic matter (OM) are generally produced in smoldering fires. OC primarily consists of scattering particles/aerosols that can be white to clear to brown. OC contributes to global cooling because it is composed of aerosol particles that reflect sunlight back into space. The pollutants can also become nuclei for cloud droplets, which reflect even more sunlight back into space, but those clouds also trap heat radiated from the earth, so the effects of clouds are complex.
In aerosols, OC does not exist in isolation; it is bonded to oxygen and hydrogen. Together, the organic compounds are called organic matter (OM). The typical OM to OC ratio is 1.5 to 2.1, but can vary widely. The GWP of OM was recently estimated as -75 times that of CO2 (i.e., a cooling 75 timesthat of CO2) [Bond et al., 2004]. Since the time of that estimate, organic carbon from biofuel combustion has been shown to be slightly absorbing, and therefore has alower (negative) GWP. According to the leading author of the previous work, a likely estimate is now -50. Research is under way to verify that value [Bond, 2007].
Finished reading the pdf document "Laboratory comparison of the global warming impact of five major types of biomass cooking stove" (10 pages)
Started reading the pdf document "Indoor Air Pollution from Solid Fuels" (60 pages)
2.1 Exposure variables
2.6 Quantitative and qualitative sources of Uncertainty
3.1 Health outcomes: evidence for causality andinclusion criteria
3.2 Excluded health outcomes
OUTCOMES WITH INSUFFICIENT EVIDENCE: Lack of inclusion does not necessarily imply inconclusive findings. Rather, it refers to a relatively small set of findings, suggesting that additional, carefully conducted studies are needed to strengthen the evidence base.
EXCLUDED OUTCOMES ASSOCIATED WITH USE OF SOLID FUEL, BUT NOTCAUSED BY EXPOSURE TO AIR POLLUTION
3.3 Evidence and exposure–risk relationships
ACUTE LOWER RESPIRATORY INFECTIONS
CHRONIC OBSTRUCTIVE PULMONARY DISEASE (COPD)
LUNG CANCER
Finished reading the pdf document "Indoor Air Pollution from Solid Fuels" (60 pages)
Started reading the pdf document "Indoor Air Quality Impact of Improved Cook Stoves in Ghana" (19 pages)
Day 6 (12/6/2012 Tue)
Sustainable household energy enterprises
Profitable value chain, Profitable with a short pay back period for the end user, Locally available and not dependent on special imported parts or materials
Finished reading the pdf document "Indoor Air Quality Impact of Improved Cook Stoves in Ghana" (19 pages)
Finished reading all documents in the folder "Indoor Air Pollution" , which contains alot of data that are incomprehensible and irrelevant to the main report.
Started reading the pdf document "Test Results of Cook Stove Performance" (128 pages)
Ghana Wood: Enclosing a fire inside a cylinder of heavy ceramic and sheetmetal does not help the fire burn more cleanly. Instead, the walls may coolthe fire initially and cause the fire to smoke a bit more. More CO and PM emitted.
20 L Can Rocket: The higher temperatures and improved mixing offlame, gases and air above the fire result in more complete combustion.
Mud/Sawdust Stove: Much more efficient than 3 Stone Fire. Use less fuel and boil faster.
VITA Stove: It features ease of construction, low cost and decreased fuel use. This type of stove seemswell-suited to emergencies. More CO and PM emitted.
Justa Stove: In field tests, it saved approximately 70% of the wood typically used for cooking. However it has a slightly higher energy consumption per session, but this is outweighed by the advantage of being able to cook multiple pots per session.
Uganda 2-pot: The first pot is 30 cm in diameter, which uses up most of the heat. The smaller 23 cm pot will not boil but instead is designed to simmer sauce while corn porridge is being prepared in the larger pot. For both pots to boil, the first pot needs to be smaller than 25 cm, or the firepower has to be increased.
Patsari Prototype: Since the pots in this version are directly contacted by the fire, the Patsari ismore fuel efficient than other stoves with griddles (eg. Justa, ONIL). However like the Justa Stove, it has a slightly higher energy consumption per session.
ONIL Stove: Field surveys found that the Onil stove uses approximately 70% less wood than traditional cooking methods in Guatemala.
Ecostove: The heavy griddle takes time and fuel to heat initially, but once warm, the stove had about the same fuel economy as other griddle stoves. However it consumes more energy than any other griddle stove per cooking session.
Wood Flame: It has nine fan speeds. The stove uses much less wood than the 3 Stone Fire and makes only 16% the CO and 2% of the PM made by the 3 Stone Fire. The cost however is astronomical (from the developing country's citizen's standpoint).
Wood Gas: This is a small camping stove, so fuel must be added piece by piece to the fire under the pot. This maneuver is abit difficult. For its price, a griddle stove could be purchased, making it rather expensive.
Mali Charcoal: Burning charcoal can emit high levels of CO. At high power, the levels of CO emitted were dangerous.
Gyapa Charcoal: The CO emitted was high while PM was reduced, compared to the 3 Stone Fire.
Propane: This camping-type stove is low powered. In Mexico, some propane stoves are not hot enough to make tortillas, so the 3 Stone Fire is used. Propane can be somewhat dangerous as old storage cylinders and stovesbegin to leak.
Alcohol - Clean Cook Prototype: Alcohol has been a popular fuel for many years. Like kerosene, it has been used on boats when propane is considered too dangerous. Alcohol stoves have a reputation for being somewhat low powered.
Kerosene: Emissions, while low, are appreciably higher than propane and alcohol.
Parabolic Solar Cooker: The solar cooker can generate over 2,000 watts of power, boiling 5 L ofwater in an average of 70 minutes. Solar cooking uses no fuel and makes no emissions. The solar cooker is the only stove tested that does not use diminishing resources to cook food. The fuel is free, as long as the sun is shining.
Stove Rankings: Boiling Time, Type of Fuel, Energy per Fuel, Carbon Monoxide and Particulate Matter Emissions, Safety Ratings, Cost to Purchase and Monthly Fuel Use.
We strongly recommend that local cooks try the proposed stove. Only cooks will know if a stove is suitable or not.
Gas has very little mass, so the few hot moleculesin the moving gases cannot transport much heat energy per volume. It takes a lot of hot gas to deliver the required heat to a pot or griddle. Forthis reason, more heat is brought to the pot by increasing both the amount and speed of the hot gases without reducing their temperature. Radiation from the fire can be important in transferring heat, but to be effective, the radiant surface has to be hot and close to the pot.
Electric fans improve combustion efficiency. The low-volume, high-velocity jets of air increase the mixing of gas, air and fire.
Propane is a clean burning fuel that produces a hot, blue flame. Propane is stored under pressure intanks. When released, the pressure causes mixing of the gas, fire and air, resulting in very little pollution.The alcohol and kerosene stoves in this study were not pressurized and were less successful at reducingharmful carbon monoxide (CO) emissions.
The jets of hot air created by electric fans improve mixing that forces the CO to interact with air and flame, resulting in more complete combustion and dramatically reduced emissions of CO. The fuel savings and health benefits should far outweigh the cost of the electricity used.
Many chimney stoves that resulted in very low emissions in the test kitchen emitted high levels of PM and CO as measured under the collection hood from the chimney exit.
The orange color of a flame comes from the radiation of particulate matter (soot) within the flame. Blue flame results from the reaction of carbon monoxide to produce carbon dioxide. So, colored flames indicate that PM and CO are reacting.
3 T’s: time, temperature and turbulence.
Time indicates that the longer the exhaust gas stays hot, the longer pollutants have to burn.
Temperature indicates that the gas needs to stay as hot as possible; the reactions stop when the gas gets too cool.
Turbulence is an engineering term for rough flow. If the air is turbulent, pollutants have a greater chance of coming into contact with oxygen so they can burn out.
Firepower is a measure of how much energy isreleased each second. More energy is required to quickly boil water than to simmer water. The most effective cooking stove should be fuel efficient atboth high and low power operation.
The ratio between the high and low firepower (high firepower divided by low firepower) is called the turn-down ratio (TDR). It is a measure of how well the stove can be“turned down” from high to low power.
A TDR of 2 means that half the fuel was consumed while maintaining a simmering temperature, compared to the amount of fuel used to bring the water to boil.
The stoves with chimneys in this study were slower to boil water and used more wood to boil and then simmer water (Figure 14). However, these stoves were mostly griddle stoves in which hot gases transfer heat through a heavy metal surface to the pots or food placed directly on the griddle. It was the griddle that caused these differences, not the chimney.
Natural ventilation is driven by air pressure due to differences in air density. If indoor air is warmer than outdoor air, the flow out of the hole in the roof can be increased. To some extent, this stack effect depends on winter and summer temperatures.
Radiation to the pot can also be increased in a fan stove because the distance between the fire and the pot is usually reduced. For these reasons, the heat transfer to the pot is increased and less wood is needed for cooking.
Wasted smoke is fuel that could have been used to cook food.
There are more efficient methods of producing charcoal that can avoid energy losses. This includes producing charcoal in stoves that burn the volatiles in biomass to produce heat for cooking and producing charcoal from crop residues that otherwise would be burned. Between 70%and 80% of the energy in wood is used to produce charcoal. The charcoal thus produced retains the same shape of the original wood but is typically just one-fifth the weight, one-half the volume, and one-third the original energy content.
The great advantage of charcoal is that it continues burning at a steady rate, without the need to constantly feed the fire, as in a wood-burning stove.
Food should be boiled for at least 5 minutes to kill bacteria before being placed in a retained-heat cooker.
Day 7 (13/6/2012 Wed)
Thermal Efficiency (aka Heat Transfer Efficiency) is approximated by measuring the amount of water evaporated; but this technique does not indicate how much of that energy is useful for cooking. Boiling off a lot of extra steam can result in a higher “efficiency” number, but it will not cook food any faster than a moderate rate of simmering.
An alternative approach called “specific consumption” replaced efficiency in the 1985 VITA International Testing Standard.
Specific consumption is the fuel used per unit of product produced. The unit of product could be bowls of cooked food and/or loaves of bread.
“Thermal efficiency” rewards the production of excess steam, while “specific consumption” penalizes it. Making excess steam results in less final product (boiled water) and is not needed for fuel-efficient cooking.
This high-energy requirement is difficult for low-powered stoves to meet, and they remain in the pre-boiling state longer than high-powered stoves. At near-boiling temperatures, a lot of water evaporates. The longer process to reach boiling point for low-powered stoves results is much more water evaporated before boiling point is reached. This makes the low-powered stove less efficient than the high-powered stove.
Increased steam production can produce high efficiency numbers even though fuel is being used for a longer period.
Problems with efficiency become even more evident when simmering water. Simmering attempts to maintain hot water (or food) at just under the boiling temperature, using the minimum amount of fuel. The most effective methods for simmering water (such as the use of pot lids,insulation, retained-heat cookers, etc.) cannot be measured by the method of estimating heat transfer from steam loss.
Getting more of the heat from a fire into the pot (improving Thermal Efficiency) can also result in more pollution. For example, lowering a pot closer to the fire results in lower fuel use but also makes more smoke.
Smith lists examples from his studies where small decreases in combustion efficiency, following changes to increase heat transfer efficiency, resulted in two to three times more pollution per meal.
In the VITA and Mud/Sawdust stoves, the fire is surrounded by a metal or earthen wall and moved closer to the pot. In both stoves, small channels force the hot gases to also scrape against the sides of the pot. They create more pollution per meal because they do not address combustion efficiency
As measured by the Enerac 3000E, the two charcoal stoves emitted about twice as much unburnt hydrocarbons as the wood-burning stoves.
Finished reading the pdf document "Test Results of Cook Stove Performance" (128 pages)
Thinking about what can be done in Cambodia:
- GERES had an established commercial route and they already had a footing in the traditional Lao stove market.
- Philippines and Vietnam both have alternatives to Lao Stove: we can learn from their endeavors to introduce Parabolic Solar Cookers and Mayun Turbo Stove to the locals.
- I notice another method of cooking still popular with Cambodians: 3 Stone Fire (probably because Lao Stove which runs on charcoal is not high-powered enough). Potential to introduce " improved wood-burning cook stoves" to them.
- There is also the briquette and biochar. Since city dwelling Cambodians mainly use charcoal as their source of fuel but still burn wood for certain cooking, producing charcoal as a byproduct (biochar-producing gassifier stoves) might greatly improve energy conservation. The biochar also has many other uses.
Day 8 (14/6/2012 Thur)
Diarrhea
Day 9 (15/6/2012 Fri)
Started reading the pdf document "Rice Husk Stove Handbook" (155 pages)
The Belonio Rice Husk Gas Stove is the first TLUD gasifier that can utilize small-particle fuel.
The Belonio Rice Husk Gas Stove can operate with remote combustion.
LPG - Liquidified Petroleum Gas
LPG is widely adopted for household use because it is convenient to operate, easy to control, and clean to use because of the blue flame emitted during cooking.
However, because of the continued increase in the price of oil in the world market, the price of LPG fuel had gone up tremendously and is continuously increasing at a fast rate.
Wood gas stove was found promising to replace the conventional LPG stove. However forest denudation combined with the need for fuel for cooking requirement, there is a need for us to look for alternative biomass fuel, other than wood, that can be used for cooking.
The rice husk gas stove development in the Philippines originated in 1986 under the DA-IRRI Program for Small
Farm Equipment. The potential it held led the DAE-CA-CPU to develop a similar technology in 1987. Various issues faced, especially in the excessive tar produced from the gasification of rice husks, led to its temporary suspension.
In 2000, with the establishment of the Appropriate Technology Center (ATC) under the Department, different designs of cook stoves were developed utilizing rice husk as fuel.
A collaboration between APROTECH ASIA and the ARECOP gave the Author was given an opportunity to attend the Training on Wood Gasifier Stove at the Asian Institute of Technology in Thailand in 2003
In the late 2004, a prototype rice husk gasifier stove following the IDD/ TLUD concept was fabricated as a
student project.
Performance test and evaluation in early 2005 showed that rice husk fuel for IDD/ TLUD gasifier was proven to be a good alternative technology to conventional LPG stoves. After six months, a commercial model of the gasifier stove was
introduced in the market for utilization. Initially, 30 units of the stove had been commercially sold (See Table 7) for reproduction and for promotion all over the Philippines.
23 tanks of 11-kg LPG fuel can be replaced by a ton of rice husks.
It will reduce the problem of rice husk disposal which contributes a lot on environmental pollution, especially burning at roadsides and the dumping along river banks.
It will provide employment and income generating projects for Filipinos in the production and marketing of the stove, and even in the selling of rice husk fuel in the future.
The rice husk gas stove emits a flammable and poisonous gas. Make sure that the gas produced during operation is
properly burned in the burner. DO NOT INHALE THE GAS EMITTED FROM THE STOVE BECAUSE IT IS TOXIC AND
INJURIOUS TO HEALTH. The stove should only be operated in a well-ventilated place.
It needs electricity to run the fan which limits its adoption in areas that are far from grid, except when a 12-volt battery and an appropriate inverter are available.
Wet rice husks will not gasify, if used. It will produce a lot of smoke and will result to inconveniences during operation
When the operation ends, shut OFF the fan to keep the smoke from coming out of the stove.
Future focus on the fuel reactor design will be on the following:
1. Rice husk gas stove operating in a natural draft mode that will operate without the use of a fan or a blower.
2. Rice husk gas stove for continuous operation - it will have a provision for loading of rice husks and unloading of char without interrupting the operation.
3. Rice husk gas stove fuel with rice husk in a canister. This makes it more convenient, and aid widespread adoption.
4. Rice husk gas stove with storage tank for generated gases – gases produced are temporarily stored in a drum so that cooking can be done anytime of the day.
5. Rice husk gas stove operating on AC/DC power – This allows the operation of the stove either on grid or on 12-volt battery, allowing more flexibility to cope power failures.
6. Rice husk gas stove made from locally-available low-cost or indigenous material.
7. Rice husk gas stove for baking and grilling.
Finished reading the pdf document "Rice Husk Stove Handbook" (155 pages)
2/7/2012 Mon
Agricultural Residues have many disadvantages as an energy feed stock
- Low Calorific value
- Difficulty in controlling of burning
- Difficulty in mechanising continuous feed
- large storage capacity required
- problems in transportation and distribution. Inefficiency is due to low bulk density of agricultural residues.
In general agricultural residues can be divided into 2 groups: crop residues and agro-industrial residues
Biomass Briquette Production: CBA
Advantage of Biomass Charcoal Briquettes over Charcoal:
- Less smoke
- Odorless
- Higher calorific value than wood charcoal
- Much lower ash content than charcoal
- No spark
- Less crack and better strength; burns longer
The biggest improved cookstove programs of the world are being undertaken in China and India. Electricity generation based on biomass combustion employing boiler-steam turbine systems is well established.
Heated-die screw-press briquetting machines are almost exclusively used in the Asian countries east of India.
In some of these countries, e.g. Malaysia, Philippines, and Thailand, biomass briquettes are mostly carbonized to obtain briquetted charcoal.
In India, Africa and Latin America, piston presses are most commonly used for biomass densification, although a significant number of screw presses are also used in India.
In Africa, large-scale briquetting plants have been established in Ethiopia, Kenya, Malawi, Uganda,Sudan, Zambia and Zimbabwe.
In Latin America, densification is best established in Brazil, which, with an annual production of about 1 million tons, appears to be biggest producer of densified biomass in the world; it appears that densification is not common in the other countries of the region.
Biomass based cogeneration technology is well established in the pulp and paper industry, plywood industry and agro-industries- eg. sugar mills and palm oil mills.
The cost of biomass fuels strongly depends on the location/country as well as type. For example, a residue like rice husk may have a cost ranging from negative values in some situations (disposed at a cost) to 10-20 US$ per ton in places where it is used for energy, or other purposes.
Practically all the biomass energy plants installed by the EC-ASEAN COGEN Programme (an economic cooperation programme between the European Commission and the Association of South-East Asian Nations coordinated by the Asian Institute of Technology, Bangkok, Thailand) are also based on cheap fuels, residues and wastes.
Compared to piston-press, heated-die screw press have smaller capacity but produce stronger and denser briquettes. Screw press technology is therefore more suitable if the briquettes are to be carbonized to obtain briquetted charcoal.
Carbonization-briquetting process: biomass is first carbonized and the resulting charcoal is briquetted using a suitable binder. Used for cotton stalk in Sudan and coffee husks in Kenya; limited use of this technique has been reported in India and Nepal. Briquetting of bagasse using molasses as binder has been reported to have had limited success in Sudan.
Another low-pressure binderless briquetting process involves mixing pulverized chopped and decomposed biomass with water into a pulp. The pulp is pressed inside a perforated pipe to get 4-inch diameter cakes,which are sun-dried to get briquettes (Stanley, 2002). The basic press is made on site and the product is normally of lower density compared with conventional briquettes. A non-profit organization, Legacy Foundation, is currently involved in dissemination of the technology.
Briquette made from a mixture of pulverized coal, biomass and slaked lime has been introduced by a Japanese company in two Asian countries, China and Indonesia. The briquettes, called coal-biomass briquettes are produced by using a roll-press. It is claimed that the use of the desulfurizing agent (slaked lime) and biomass results in cleaner combustion of the briquettes in stoves and less of ash compared with coal or coal briquettes (Kobayashi, 2002).
Sawdust is the dominant raw material in Malaysia, Philippines, Thailand, and Korea.
Rice husk is the only raw material used in Bangladesh.
Peanut shell and cotton stalk appear to the most important raw materials in Africa.
The cost of a locally made briquetting machine in Bangladesh has been reported to be about Taka 50,000 (60 Taka ~ 1 US$). The technology appears to have been developed by the local entrepreneurs without any support from the government or donor agencies.
The capacity of screw press briquetting machines is about 100-120 kg/hr.
The capacity of piston presses normally lies in the range 400-2000kg/hr (Vempathy, 2002)
Initially, rice husk was practically the only raw material used for briquetting and it was available almos tfree of cost; this created a lot of interest in briquetting and establishment of more briquetting plants uptoabout 1991. Later, cost of rice husk increased due to demand for alternative uses; because of this and a number of other reasons many of the briquetting plants, including practically all of the carbonization briquetting type, were ultimately closed down. At present only six briquetting plants are in operation inNepal (Shakya, 2002).
Practically all types of densification machines have been tried in Africa
- imported screw presses for briquetting sawdust in Eritrea, Malawi, Tanzania and Ghana
- piston presses used for briquetting coffee husk in Kenya and groundnut shell in Sudan
- pellet presses for densification of ground nut shells in Zimbabwe and Senegal and sunflower husk in Zambia.
- ABC Hansen A/S have established nineteen briquetting plants in several African countries, e.g. Burkina Faso (1), Eritrea (1), Ethiopia (7), Gambia (1), Ghana (1), Kenya (2), Nigeria (1),Rwanda (1), Sudan (4), Zambia and Zimbabwe; it appears that more than half of these are still in operation.
- Besides, conventional binderless briquetting, low-pressure cold briquetting using binder has also been tried in some places.
It appears that tw omore attempts to introduce biomass briquettes in Nicaragua were made in the past. One of these used cotton trashes as the raw material, while the other used sawdust; the briquettes were found to be costlier than fuelwood and did not find market-acceptance (Engracia, 2002).
In general densified biomass is not cheap and cannot compete with fuelwood in developing countries. For example in Kathmandu, the capital of Nepal, the price per kg of briquettes is about three times the cost of fuelwood (Shakya, 2002).
However, although briquettes are normally costlier compared with fuelwood,these have found some acceptance under some special situations:
- Reliability of fuel supply
- Consistent fuel quality
- Eco-friendly image
- Superior Quality:
Fuelwood may need further preparation (sizing and drying) before actual use, briquettes are directly used and can be easily broken to pieces of desired length if needed.
A piece of biomass briquette burns for a longer period compared with a piece of fuelwood of comparable size
A survey in Thailand established that food-vendors preferred briquetted charcoal obtained from carbonization of sawdust briquettes over wood-charcoal because of it superior properties: longer lasting fire, consistent quality and non-sparking combustion (Bhattacharyaand Shrestha, 1990)
- Low price: Free raw material, low-cost briquetting technique and special situations may make briquettes cheaper than alternative fuels. In India, briquetted biomass is competitive in places where coal is expensive because of long transportation distances involved.
Barriers to biomass briquetting in Bangladesh included
- lack of awareness about the technology (among potential entrepreneurs)
- lack of stable supply and price of raw materials
- operation and maintenance problems
- lack of trained technicians
In Myanmar, the barriers included:
- lack of appropriatefinancing mechanism (for business establishment)
- lack of availability of suitable systems/machines.
Based on a study of the briquetting industry in India, frequent failures of power supply in some developing countries may also present a barrierto smooth and profitable operation of briquetting plants (Clancy, 2002)
High cost of briquettes compared with fuelwood in most developing countries is also a barrier to acceptance of briquettes in most developing countries.
Common barriers:
- Bias in favour of conventional fuels and energy systems
- technical problems
- need for significant storage space
- initial investment needed for change-over from the existing heating system
A compression ratio of approximately7:1, the loose biomass to form briquettes.
Although there are a number of different briquetting technologies commercially available, the challenge is to find a technology which is suited to the local market, both in terms of the briquetting press itself for local manufacture and the briquettes.
Entrepreneurs in India, which have mainly used the piston extrusion presses, have not been a complete success because of the variation in raw materials and a numberof socio-economic constraints.
Sometimes the briquettes have been found difficult to ignite or burn slowly, with high levels of smoke. Also because of irregular production patterns, arising from the intermittent breakdowns of the briquetting machines, the briquettes have not been able to penetrate the fuel market in the industrial sector.
In a piston press, the wear of the contact parts (eg. the ram and dies) is less compared to the wear of the screw and dies in a screw extruder press.
The power consumption in the former is less than that of the latter.
However, in terms of briquette quality and production procedure the screwpress is superior.
The central hole in the briquettes produced by a screw extruder helps in uniform and efficient combustion, with significant reductions in smoke.
Local manufacture of the press is an important factor in guaranteeing the sustainability of the technology, by ensuring that the skills for maintenance and after-sales service are indigenous and hence readily available.
A criticism levelled at imported technology is that real technology transfer does not take place, which rapidly leads to equipment being either abandoned or operated inefficiently.
Briquetting and/or carbonisation plants – especially when run on a large scale basis – require a stable supply of raw materials which could only be granted by large farms and frequent harvesting campaigns.
Success also depends on good access tothe customer, whether it is supplying to a few large scale consumers or to a great number of small consumers.
People are only willing to change to a new fuel if it is reliable, convenient and cheap.
Small scale production and application of fuel from agricultural, forestry and urban organic waste seem to have a comparative advantage over large scale, because
- they require less investment,
- are flexible inrespect to fluctuation in raw material supply, type and quality,
- are often poverty driven, which lowers the acceptance barrier against the new fuel.
A thorough investigation into the availability of raw material, the consumer habits, the access to technology and thelimiting cost factors is compulsory before starting briquetting and carbonisation projects.
3/7/2012 Tue
Sources of Raw Materials: Field Residues, Process Residues, Domestic and industrial organic waste
Field Residues:
- maize, wheat, rice, millet, sorghum straw
- cotton residues, banana leaves
- forestry residues like dead trees, leaves and branches, reed and sedge, weeds
Process residues:
- Sugarcane bagasse
- coffee and rice husks
- coconut and groundnutshells
- coir dust
- tree barks, saw dust and shavings
- charcoal dust
Domestic and industrial organic waste:
- waste paper and cardboard
- furniture waste
Depending on the amount of raw material available, the type of fuel to be produced and the availability of funds and technical know-how, different shredding, briquetting and carbonisation techniques are applied.
Due to the large variety of agricultural, forestry and domestic organic residues and a limited number of briquetting (and carbonisation) techniques it is important to homogenise and condition the feed material for the subsequent processes.
The most important conditioning step is shredding. Only small size particles and homogenous material are adequate to be fed into the compaction device. Material with a high water content (e.g. reed,sledge) is much easier to dry after shredding.
Depending on the brittleness of the raw material (e.g. coconut shell compared tofresh leaves or straw), hammer or cutting mills are used for shredding.
The briquetting technologies can be divided into:
• High pressure compaction
• Medium pressure compaction assisted by a heating device
• Low pressure compaction with a binding agent (aka Low Pressure Cold Briquetting)
Depending on the type of material, the pressure applied and the binder used, different binding methods are used.
The physical properties (moisture content, bulk density, void volume and thermal properties) of the biomass are the most important factors in the binding process of biomass densification.
The densification of biomass under high pressure results in mechanical interlocking and increased adhesion/cohesion (molecular forces like van der Waal’sforces) of the solid particles, which form intermolecular bonds in the contact area.
Additives of high viscous bonding media (binders), such as tar, molasses and other molecular weight organic liquid can form bonds very similar to solid bridges. Adhesive forces at the solid/liquid interface and cohesion forces within the solid are used for binding. Lignin of biomass/wood which is deliberated under high pressure and/or temperature can also be assumed to help binding in this way.
Apart from lignin, which is gained from the feed material itself, other free atoms or molecules (eg. moisture) can be attracted from the surrounding atmosphere to form thin adsorption layers. They also support the formation of bonds between the individual particles.
High and medium pressure compaction normally does not use any additional binder.
Other briquetting technologies are less applicable in developing countries because of high investment costs and large throughputs (eg. roller-presses to produce pellets or briquettes)
4/7/2012 Wed
Organic binders: Molasses, Coal tar, Bitumen, Starch, Resin
Inorganic binders: Clay, Cement, Lime, Sulphite liquor
Hand moulds are the simplest devices to form small quantities of briquettes. Used in Mali for the production of briquettes from waste charcoal dust and molasses as binding agent.
The briquettes reach their final strength after drying in the sun or a gentle heat treatment in a curing furnace.
A wide spread semi-mechanised method to form briquettes from mineral coal is found in China. Ground coal is mixed with water and approximately 20% of clay binder and formed into so-called honeycomb briquettes by a mechanised
briquetting press.
In Kenya and Benin, biomass of fine particle size (saw dust, rice husks, wood shavings, charcoal dust, etc.) was mixed with approximately 20% of (waste) paper pulp and formed into briquettes in a manually operated piston press.
The production of carbonised briquettes from agricultural residues may follow two possible production sequences:
a) Carbonisation → grinding → briquetting
b) Grinding → briquetting→ carbonisation.
Coarse material of medium size (coconut and groundnut shells, tree bark or briquettes fine material) is carbonised in continuously working shaft furnaces.
Carbonisation of fine material takes place in rotary kilns or stationary vessel equipped with a stirring device (eg. a screw feed).
3 ways of valorization are considered:
- Gasification for thermal and electrical applications
- carbonization for char
- briquetting activity and densification for biomass briquetting activity.
In Cambodia, artisanal/small scale activities are preferable to industrials.
There are 2 types of Charcoal
- Renewable charcoal: For each tree cut down to fabricate it, a new one is planted.
Hence the CO2 emissions of this renewable charcoal are absorbed by the new trees planted; the outcome is carbon neutral.
- Non-renewable charcoal as there is no biomass management; trees are not replanted.
The CO2 emissions can’t be reabsorbed by the new trees, the cycle is broken and the balance becomes carbon positive.
The charcoal market need to establish financial compensation to restore carbon neutrality. The combustion of 1kg of this charcoal is 2.74kg of CO2*
Cambodia has few conventional energy sources available. However, there are some potential renewable energy sources like hydraulics. Fossil fuels are all imported.
Wood represents 80% of the energy used.
93.1% of energy derived from wood and charcoal are used for cooking.
Small Production Activities:
- Noodle Production
- Palm Sugar Production
- Rice Wine Production
- Bread Production
- Restaurants
Industrial Activities: Brick Factories
Main Fuel used for Small Production & Industrial Activities: Wood, Rice Husk
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