Biogas in Nepal: Report from National Geographic Reconnaissance Trip

Biogas Support Program

T.H. Culhane

Hinku Valley

Executive Summary:

Over the past two springs, on a Blackstone Ranch Foundation/National Geographic Innovation Challenge Grant to the Khumbu and Hinku Valleys of the alpine Himalayas, Dr. Thomas Culhane worked with Dr. Alton Byers, Chris Rainier and the Mountain Institute's Anrita Sherpa to assess the potential for replacing  endangered juniper shrub, forest timber resources and kerosene and bottled gas with renewable, net-carbon-free and inflation resistant technologies.

It was determined that while parabolic solar cookers, vacuum tube and flat plate solar thermal systems, photovoltaics, wind power and micro-hydro power all have a role to play in the transition away from the combustion of carbonaceous fuels, none of them, alone or in combination, have the capacity to free the growing populations of the region (particularly given increasing tourist loads) from the traditional fuels. Interruptions in supply and price volatility of fossil fuels, which require a lot of transportation logistics as well as being exogenous and subject to political conflicts, lead to continually renewed dependence on local biomass, while the intermittency of sun, wind and water based renewables make them only partial solutions.

What is needed is a base-line solution that can “fill the gaps”  between the production lows of the renewables already making their way into the valleys  and times of market scarcity for fossil fuels so that families and lodge operators can have reliable fuel for cooking and heating. In Nepal the obvious answer would appear to be biogas.

Nepal's BSP (Biogas Support Program), run in conjunction with The World Bank, KfW Germany, The Government of the Netherlands and The Government of Nepal, has been tremendously successful in its outreach effort to the lowland areas of the country, training people to install over a quarter million small scale biogas digestors throughout the country in the last decade. The BSP has also begun working on high altitude biogas pilot projects and has found no technical barriers – they successfully demonstrated the utility of digesters that used insulation, compost heating and warm water feeding to maintain the proper temperatures for effective use.

Two awareness problems have stood in the way of the continued expansion of this program up into the higher altitudes. The first is an unfounded belief that biogas systems require a constant source of animal dung and therefore reluctance to use them where other uses for animal dung are cited, or where animals are scarce. Most people are simply unaware that the superior feedstock for biogas systems, per unit kilogram of feed, is actually something that creates a nuisance and environmental hazard in the tourist regions of Nepal: food waste.  The second is a simple lack of familiarity with the systems and their robustness, and so investment is simply not made in the construction materials even though operation and maintenance costs are so low.

Besides taking an inventory of the current installed capacity of the solar electric, solar hot water, wind and micro-hydro systems in the two valleys, we began an awareness building campaign with the local lodge owners.  Ang Rita Sherpa of the Mountain institute took Culhane to several meetings with lodge owners to do presentations on the potential for biogas and there was a high level of interest and excitement. Particularly exciting to many of them was the potential of biogas digesters not only to turn all of the food wastes into clean burning methane and fertilizer, but to do the same with all the toilet wastes currently threatening the regions freshwater resources.

It would appear that interest and awereness are, in fact, growing: Recently, a reporter working for WIRED and National Geographic Magazines sent us a story pitch, describing a new project he wants to write about, meant to deal with the hazardous accumulations from fecal material in Gorak Shep, the last village on the heavily trafficked route to Mt. Everest:

Story Pitch-A biogas reactor on top of the world-Pitching to WIRED Science-

The tiny village of Gorak Shep has a very messy problem.

Nestled in the shadow of the world’s tallest mountain, the community is literally running out of space to put human waste brought down from the Everest, Pomori, Lhoste, and Nupste basecamps.  More than 13 tons of human fecal matter is annually dumped into open pits at Gorak Shep and it is contaminating local water supplies. (Managing Sanitation in Protected Areas-Mt.

Everest guide Dan Mazur is working with a group of Washington State-based engineers on an innovative solution to the problem. They are designing a biogas reactor to convert feces into cooking fuel for the inhabitants of Gorak Shep. At nearly 5,200 meters, it will be the world’s highest elevation bio gas reactor upon completion in late 2013 (

The project’s technical lead, Robert Spurrell, a former director of R&D for the Weyerhaeuser Company (, says the team will complete designs early next month for a greenhouse enclosure to raise temperatures inside the reactor to 30 C from the ground temperature at Gorak Shep of around 10 degrees C, too low for biomass to be converted to methane and carbon dioxide.

Mazur says several Nepalese communities near Everest are onboard and excited about the project’s potential for future development at Gorak Shep and further down the mountain.

Our team was asked by the reporter to comment on the feasibility of the project.  Our analysis was that a high altitude digestor of sufficient size, if well enough insulated, can definitely eliminate contamination from fecal waste, and can create valuable fertilizer, however the energy value of the toilet wastes will most likely be  insufficient to do many useful things with the gas.  We have recommended that all the food wastes be added to digester. To ease the process have offered to donate a bicycle powered Insinkerator food waste grinder that the engineers at Insinkerator developed for us when we returned from Nepal after trying to run a unit on Solar energy and burning out the inverter.   The new unit can be powered either by a person on the bike or by electricity when it is available and yields 24 hour methane at sufficient volumes that Gorak Shep can turn its ever increasing tourist load and their wastes into an asset rather than a liability.

Meanwhile, tests at Culhane's residence in Germany through the winter have shown that hot water feeding through an in-sink food grinder, coupled with circulation of bath and shower water (heated by solar evacuated tubes or natural gas) is sufficient to keep the biodigester productive throughout the lowest temperature events. We are thus confident that replication of this model in Nepal could be rapidly and successfully achieved with  initial investment to build insulated digestors, build greenhouses around them, provide or make use of solar hot water for tourist bathing by redesigning the plumbing so that waste hot water flows through the digestors and by redesigning  toilet facilities so they flow into the digestor or deposit into compost heaps that can be added to the digestor. With food wastes as the major feedstock and toilet wastes contributing there is no reason to ever be without a reliable supply of gas and fertilizer during the seasons when people are in the area – the more tourists, the more feedstock and hence gas and fertilizer we would be able to produce.

The technology is all there. It is now merely a question of interest, will and investment.

End Executive Summary


The following is a portion of the full text of the report, which can be found illustrated with photographs at:


The problems:  Deforestation and Indoor Air Pollution

Despite a successful  ban on the collection of the slow growing shrub juniper and its replacement with kerosene and despitee the growing penetration of photovoltaics in the Hinku Valley of Nepal  (roughly 2 kilowatts of installed capacity throughout the valley with an average of  20 Watts per lodge) and the presence of 4 solar cookers (2 in each of two villages), the fate of the forest and general alpine ecosystem is still very uncertain.


Additionally,  indoor air pollution is still a major health hazard, claiming lives and causing respiratory and eye illnesses as well as cancer, particularly among women and children.  Firewood continues to be the primary fuel used for both cooking, heating bathing and washing water, and for keeping the homes and lodges warm.

The Hinku doesn't have large yak populations so yak dung for these purposes is in short supply, and even in areas like the Khumbu Valley where there are still substantial yak populations, yak dung, while a sustainable fuel from a production and consumption standpoint, still causes great discomfort and suffering through air pollution when used for combustion.


In summary, as  Balgain and Shakya (BSP report 2005) point out

"The heavy dependence on fuelwood resources has a negative impact on the environment resulting in deforestation around villages and the deterioration of soil stability on the affected hillsides. In addition, the burning  of dung reduces soil fertility.  With deforestation around villages, the daily labour required for collecting  fuelwood increases impacting primarily women and children and leaving little time for education as well as for productive tasks. Additionally the smoke  emitted from the burning of the biomass has adverse health effects on women and children causing widespread eye and respiratory diseases." (p. 6).

The kerosene that has replaced shrub juniper in the highest alpine areas carries with it its own health risks (the hydrocarbon smoke and fumes are both poisonous and carcinogenic) and carries with it substantial economic risks (prices can fluctuate wildly as the supply comes from India and relies not only on price and social stability there but on an entire supply chain that must get the fuel parsed into appropriate containers and transported for many days through the narrow passes up to the mountain villages.)

The Sun as Solution

There is a widespread belief that solar energy can provide the solution to the energy problems faced by people in remote areas, and this is true but only if all forms of solar energy are considered, including organic wastes.  The naive assumption that electricity, whether derived directly from the sun through photovoltaics, or indirectly through wind power or hydro power, can provide the answer  inhibits real solutions from being implemented.

The "energy-ladder" assumption that electricity is considered the apogee of energy development has been called into question when full environmental and cost accounting is done (see "From Linear Fuel Switching to Multiple Cooking Strategies: A Critique and Alternative to the Energy Ladder Model" by Masera  Saatkamp and Kammen, 2000). Instead, as Masera, Saatkamp and Kammen point out, "rural households do not ``switch'' fuels, but more generally follow a multiple fuel
or ``fuel stacking'' strategy by which new cooking technologies and fuels are added, but
even the most traditional systems are rarely abandoned."  To help solve the problems in highland Nepal we need to understand how local people weigh the costs and benefits of any given technology and consider with them what the best mix might be at any given time.

Westerners accustomed to using electric water heaters, electric space heaters and electric stoves usually do not understand that converting electricity into heat is the least efficient use of this energy medium and that electrical resistance heating uses so much electricity that it is nearly impossible to deliver on a material or cost-effective basis for poverty alleviation.

Electricity generated in remote areas, whether via fossil-fuel powered gensets, or any of the renewable sources, has been found to be insufficient for sustainable cooking or heating;  its appropriate use is for lighting, communications and computer equipment and power tools.

For all forms of heating where electricity is in limited supply or costly, people will continue to use wood, charcoal, biomass (like dung and brush) or liquid fuels (like petrol, diesel or kerosene) unless we can supply them with more efficient direct forms of heating.  Even in areas where reliable micro-hydro electricity has been developed, for example  in the Khumbu valley and around Lukla,  there are seasonal outages and rationing and problems with siltation and most lodges must rely on backup generators just to provide lighting. We experienced frequent interruptions in electric service on this expedition when we were staying in Lukla.   Climate change and disruptions of the normal cycles of glacial buildup, thaw and melt will increase the challenge of year-round reliance on hydroelectricity as an answer to all energy needs, even where it is available and well developed.  Thus, other options must be made available to create a diverse portfolio of solutions that is resistant to disruption.

Solar Water Heating (SHW), particularly through the use of highly efficient vacuum tubes which quickly create hot water ranging from 80 C to 110 C, is  a marvelous solution that is easy to implement in the Hinku as we discovered during the 2011 expedition to Dingboche (one must merely be careful to pack glass tubes very carefully and securely for transport and ensure that nothing can fall on them once installed).  SHW is ideal for bathing;  for cooking purposes solar hot water can also be used, usually as preheating solution  to get the water from its ambient temperature in the region (normally between 0 and 15 C) to temperatures well  above 50 C. Using SHW for base energy it then takes very little additional fuel to get it to boil.


Greenhouse heating as an adjunct to space heating is a very plausible answer to mitigating the use of forest resources but  has not been observed despite the presence of two green houses in the Hinku Valley -- these were detached from the lodges so the heat was not utilized for human habitation.  Nonetheless the possibility exists with some awareness training and examples. 

Other forms of solar space heating (passive solar architecture, the construction of solar space heaters using black paint coated aluminum cans in a glass box piped into the house and facing South) have not been observed in Nepal but could be easily implemented; interestingly none of the houses or lodges we observed in the Hinku valley were oriented to use the sun's light or heat; there were no south facing windows to permit solar gain, no thermal masses used to retain solar heat; nothing in the construction of the lodges or homes seemed to be designed to permit heat gain or avoid losses.

Anrita Sherpa from the Mountain Institute pointed out to many of the lodge owners in the Hinku how his brother in Naamche Bazaar, who uses solar vacuum tube systems, solar cookers, heat exchanging efficient stoves, on-demand propane gas heaters, photovoltaics and large south facing windows, also insulates his lodge by placing hundreds of recycled PET water bottles between the stove walls and the plywood, creating a dead air space that keeps most of the heat in and reduces the need for fuel.

Insulation may be the single most important and easy to implement immediate solution for direct reduction of woodfuel in the Hinku.  Besides this, the use of mylar reflective sheet to keep heat inside the lodges would also have a profound effect.  In this case one would be applying the principle used by emergency "silvered" blankets to save people from hypothermia and the principle used by the inside of thermos containers.


Foodscraps and human and non-human bodywastes: reliable sources of solar energy through biogas

In our opinion, concerning the transition away from burning biomass or fossil fuels, the simplest solution to both the environmental and the health challenges posed by firewood and kerosene is the use of biogas.

Biogas is an oft neglected form of stored solar energy that nonetheless can be made available 24 hours a day, 7 days a week, 365 days a year, come rain or shine.  If the Cole Porter song "Night and Day, you are the one..." were rewritten to speak about the potential for renewable energy, it would be speaking about biogas.

Rather than falling on solar thermal panels or vacuum tubes  to heat up water which must be stored in a hot water tank, or on photovoltaic panels to create electricity which must be stored in batteries, biogas production depends on sunlight stored in the chemical bonds of organic material -- plants and animals, fungi and microbes, and the waste products they produce.

In general the cycle is very straightforward: sunlight is absorbed by plants in a farmer's field, humans and animals eat the plants and convert some of the stored solar energy into movement and growth and excrete some as their manures.  A significant portion of the stored solar energy that was converted into chemical bonds through photosynthesis is  contained in plant parts that humans and animals do not eat or is in left over food scraps, and this reliable and easily obtained form of sunshine is simply thrown away in the garbage, paradoxically creating health and hygiene problems.

All of that stored solar energy, whether in the hydro-carbon bonds found in human and animal wastes, plant wastes or left-over food wastes, can be easily converted into methane gas (CH4) by anaerobic bacteria and Archaea that are ubiquitously found in the stomachs and intestines of all animals as well as in lake and pond mud all over the world. The procedure for creating biogas is deceptively simple: one simply creates an "artificial stomach" from any kind of container (plastic, cement, mud, canvas, leather...) fills it with water and any source of the abovementioned bacteria, and fits to it a feeding tube that goes under the water level into which organic waste can be fed, and effluent tube that comes from a spot a little higher than the feeding tube, but still underwater, and a gas outlet tube that comes from the topmost part of the "stomach" where the lightweight biogas will accumulate.  That is it. There is no secret and no special technique that needs to be applied.  The microbes do the rest.

One can always improve the gas production by finding ways to increase the surface area inside the artificial stomach (we use hundreds of small plastic cylinders like the "bioblocks" found in pond filters that permit biofilm growth) and one wants to make sure not to overfeed with food waste lest the stomach get too acid -- the bacteria need a neutral pH.  Similarly, to work properly the bacteria need to be kept between 20 and 40 degrees Celsius, but this are trivial plumbing and insulation and feeding rate concerns, not any kind of rocket science.

In fact biogas production is probably the simplest and most efficient way that any human being, family or community can make good use of solar energy immediately. Everybody has the main ingredients (the bacteria live in our own guts and can be obtained from our feces, and everybody has food wastes of some kind).

Where people are still burning wood and charcoal and suffering from the effects of indoor air pollution and deforestation we must ask ourselves what the reasons are that this easiest of technologies has not yet been implemented in their community. 

Biogas in the fight against indoor air pollution in Nepal

Nepal has a long and successful history of biogas training, installation and use and is one of the few countries to have several agencies dedicated to dissemination and improvement of this radically simple and effective technology.

Nepal supports biogas principally in a effort to stop the suffering and mortality caused throughout the country by indoor air pollution.  A secondary priority is the ability for biogas to help curtain deforestation. However, as EPA director Lisa Jackson told a group of us at the Aspen Energy Forum in 2011, if we focus on end-goals that have broad support and appeal (like stopping deaths of women and children from indoor smoke) we will also achieve the other goals (stopping reliance on firewood and charcoal which exacerbate deforestation).

Across from the United States Embassy in Kathmandu on the second floor of a small building complex  is the  office for  "The Partnership for Clean Indoor Air" . Their mandate is 

Project 1: Improving Households Energy Management Practices in Sacred Himalayan Landscapes, Langtang National Park-Rasuwa Funded by GEF/UNDP Small Grant Programme
Project 2: Advocacy for Gender Sensitive Energy Policy in Nepal funded by ENERGIA Network

They are partnered with an International Organization, orignally UK based but now with offices in Bangladesh, Kenya, Peru, Sri Lanka, Zimbabwe, Sudan and Nepal called "Practical Action".

In 2009 Practical Action Nepal published a book called "Inventory of Innovative Indoor Air Pollution Alleviating Technologies in Nepal" which primarily covered improved cookstoves and solar cookers, but which had a chapter on "biogas technology" as disseminated  in Nepal.  I visited the office in Kathmandu and they kindly gave me a copy which is also available in its entirety as a .pdf on the web.

Nepal has already successfully introduced more than 250,000 domestic biodigestors in their country of some 30 million people and the technology is well known throughout the lowlands. Through awareness campaigns and targeting subsidies the number of digestors is growing daily.  Only in the Himalayan communities is the biogas solution either still unknown or considered "difficult" to implement.

Nonetheless everybody I met with in Nepal who is involved with biogas seemed to think that high alititude biogas is both  important and doable.  In fact they have been testing several systems in high altitude with good results. The Practical Action report states, 

"A research is undertaken to develop appropriate biogas plant designs for altitude higher than 2,100 m.  Two plants were installed during the 3rd Phase in Khumjung and Lukla of Solukhumbu district with greenhouse technology. However,despite the merit of the design and technology, the project cost was very high.  Four years ago, three other simpler new designs were tested in Beni VDC of Solu district with much lower project cost. One of the three designs, a simple addition of heap composting on top of the digestor is found to be the most appropriate and cost-effective design. This design is thus widely promoted between 2,100 and 3,000 m altitude as part of the regular national programme with subsidy. The GGC-2047 design with heap composting  technology was approved for commercial dissemination last year. Till date, some 40 biogas plants with heap composting are constructed in upper part of Rasuwa district and more are under construction. Some 30 plants with such heap composting are installed in Solukhumbu district.  The results are satisfactory. BSP-Nepal is going to undertake more promotional work in remote districts of Karnali and other areas like Manang and Mustang for construction of biogas plants with heap composting  technique.  Further research was initiated in 2007 in Rasuwa district (Langtang area) between 3,000 to 3,850 m using modified GGC-2047 (improved design with provision of multiple feeding , heap composting and warm water feeding."


Since 2003 Nepal has had a robust "Biogas Support Programme" (BSP) which is a "Development Cooperation among AEPC (The Government of Nepal Alternative Energy Promotion Center), SNV (The Government of Netherlands Netherlands Development Organization), the kfw Entwicklungbank (Government of Germany German Development Cooperation) and The World Bank.


The BSP has published a very useful book on the success of Nepal's biogas program, which is available as a .pdf here:  "The Nepal Biogas Support Program: A Successful Model of Pulbic Private Partnership for Rural Household Energy Supply" written by Sundar Bajgain, Indira Sthapit Shakya and editted by Matthew S. Mendis. It is filled with great graphs, facts and figures, including success measurement indicators on a social level, as well as  designs and economic and financial assessements. 

As mentioned  Nepal has currently installed more than a quarter million home scale biogas digester systems, most of them directly thanks to the BSP and installed  during the first two phases of their BSP program. 

If there is an area that needs to be strengthened in Nepal concerning the provision of low cost clean and renewable energy through biogas it is the adaptation of these systems to the colder high altitude regions of the country, precisely where we are doing our studies.   This is acknowledged in the BSP report.

Sometimes it is the extra cost associated with building a well insulated digester and maintaining its temperature that is cited, other times it is the difficulty of transporting the building materials to the remote areas through narrow and difficult mountain passes, and sometimes, when people understand that digestors can be built with the same lightweight plastic water tanks or sillage bags available in their communities and that lightweight styrofoam insulation is adequate to keep them warm once heated, and that a combination of solar thermal heating and warm water feeding and compost heating are viable solutions to create that heat,  the usual barriers cited are worries that their isn't enough feedstock to make investment in biogas digesters worthwhile.

The belief that animal manure is necessary for biogas production

All over the world it has been successfully demonstrated that almost all organic material can be made suitable for biogas production.  In  the Mukuru slum of Nairobi we have visited public toilets that produce cooking gas for a neighboring restaurant and in the city of Pune India the Appropriate Rural Technology Institute has appropriated rural biogas digestors, made them smaller and proven that kitchen garbage is actually a simpler and more effective feedstock.  In China Puxin biogas company is showing with its new design that grass and leaves can also be used effectively.  The Culhane household in Germany produces biogas every day for cooking from a porchtop digester that is fed through an Insinkerator brand food waste grinder attached to the kitchen sink and they find that the food scraps produced by a family of 3 alone is enough for daily cooking. The Culhane's have also successfully produced useful biogas from their child's diaper wastes.

Nonetheless, in  many countries including Nepal the criteria for embracing biogas has been based on a belief that one needs a certain number of stable-fed livestock in order to get sufficient feedstock for useful gas production.

The BSP booklet states:

Both Hindu and Buddhist religions have a very positive attitude about cattle. They
attach no stigma or cultural inhibitions to the handling of dung coming from cattle or
buffaloes. The cattle are highly valued and as a result, they are seldom sold. They
are kept close to the farmhouse and in many cases are stable fed during prolonged
periods when land grazing is not practical.

The conditions in which cattle are raised in Nepal are thus ideal for providing the
animal dung, the feedstock necessary to fuel small farmer based biogas systems,
Permanence of cattle and the family attending the cattle guaranties an adequate and
a continuous source of feed for the biogas systems.

Only small size (4-10 m3) biogas systems, using cattle and buffalo dung, have been
promoted to date in Nepal. The widespread ownership of cattle provides a good
indicator for the potential of biogas in Nepal. Although some families have only one
cattle, most small farmers have two cattle or buffaloes, which is the minimum
number required for feeding the biogas systems of 4m 3 capacity.

These cultural norms have been key factors in the success of lowland biogas in the country.
But because areas like the Hinku valley have few animals, and in the Khumbu the yaks are free ranging, it has been considered impractical to gather their dung for active biodigestion.  The general design of biodigestors promoted in Nepal (the GCC 2047) and its minimum size (4 m3) discourages the use of this simple technology by families that may have only one cow or yak, even though a single animal could provide enough dung on a daily level for a 2m3 digestor which would yield up to two hours of cooking fuel per day, adequate for many small household.  Meanwhile, though ARTI India has proven that even a 1m3 digestor, made from plastic water tanks, when fed with as little as 2 kg of  kitchen waste or other sugary or starch rich organic waste, can supply a family with anywhere from a half an hour to two hours of cooking fuel per day, this option has not generally  been on the table with development agencies.

The idea of using food scraps from the lodges has not been considered in the highlands of Nepal until recently and for this reason there has been inadequate attention to urban and high altitude installations of systems.

Solar CITIES Egypt's Hanna Fathy and I found the same situation in Rwanda and discussed this with SNV, who support the project there as well as in Nepal.  We were told that SNV had tried  food waste based systems but had a poor experience when families believed they could increase the amount of gas they were getting from a small fixed sized system by simply putting in more food waste; the systems went acid and stopped producing gas and there wasn't sufficient followup to teach them that the systems will often recover if left to sit without feeding and can be put back into service by neutralizing the pH with calcium carbonate or sodium bicarbonate or some other alkaline solution (wood ash would also work) or by simply adding more manure or human toilet wastes and waiting for several weeks. It was considered simpler to restrict the program to people who had animals since animal wastes are pH neutral, contain the bacteria necessary for the reaction and can be added in unlimited amounts and so are ideal for families with livestock as a feedstock, even though the energy content is tens to hundreds of times lower than food wastes.

The last two days of our expedition while in Kathmandu I had meetings with the professors and students at Tribhuvan university (who remembered me from last year), the head of the Nepal Biogas Support Program (BSP) and the head of Practical Action Nepal. They kindly supplied me with lots of publications to read on the airplane and we had long discussions.  

With BSP and Practical Action  engineers and outreach specialists  I had productive  discussions about specific techniques we should be pursuing to keep the digesters warm.

The use of the compost toilets for heat is one they recommend, and this is something Solar CITIES also  recommended in the first Moutain Institute/Blackstone Ranch/National Geographic Expedition to Nepal in 2011 so we are on the same page there. They also recommend the use of vacuum tube solar for the "warm water feeding" of the digestors. This is something we started in Dingboche with the installation of a 15 vacuum tube SHW system on the roof of the Mountain Institute Information Center in the village and a workshop we conducted on how we could use the 80 C hot water it produced each day, through the In-Sink  Food Waste Grinder that Insinkerator corporation kindly donated, to warm water feed the digestor and keep it at temperature.

In Dingboche we were able to prove that even over 5000 meters the less expensive vacuum tube solar hot water systems performed well and could supply reliable heat for a digester; the only bad experience with the system we had was when a strong wind blew the cold water tank down from above the system and smashed some of the tubes.  Because the cheaper systems lose all of their water if a single tube breaks the system must wait for replacement tubes before continuing to operate.  The more expensive "heat tube" vacuum systems, like the Culhane's have on their roof in northern Germany and like the systems on the Italian funded Solar Pyramid en route to Everest Base Camp, continues working even with several broken tubes, and would increase reliability if the budget permitted, but the inexpensive systems are perfectly adequate (this is in contradistinction with the flat pate solar hot water systems which reflect much of the sun's heat early and late in the day and tend to experience burst copper pipes at extreme altitudes due to thermal expansion and contraction).

With good insulation (easily achieved with light weight styrofoam) the temperature in a digestor fed by a small vacuum tube solar hot water system like the one we installed in Dingboche over 5000 meters  (costing no more than $200) should stay between the required parameters (20 to 40 C) to produce reliable biogas. These digestors can be built from 1000 or 2000 liter plastic water tanks and insulated with styrofoam.

Besides small plastic digestors, another option is the one time investment in a large cement community digester like the GCC 1047 that the BSP supports, or the Puxin digestor cited in the Practical Action manual, which Solar CITIES recently built in the Philippines in a remote jungle village. Once the fixed costs of materials and transportation for cement (35 sacks, 40 pounds each), sand (obtained lcoally) and gravel (obtained regionally) styrofoam and the Puxin steel molds is paid for, the systems have a lifetime of over 30 years. These can be built underneath the compost toilets and can be connected to solar hot water systems; the technical challenge is actually simpler than transporting rock and cement and timber to build the typical sherpa homes and lodges and toilet and sheds.

Another option for keeping high altitude biodigesters at the appropriate temperature and making good use of the nutrient rich fertilizer they create is to build them inside a greenhouse structure. In Khote we found two operating greenhouses uses a simple plastic sheet for its greenhouse effect. One greenhouse was next to the Mera Lodge for convenience sake but the heated air was not being used to assist with space heating in the lodge; the other was down near the river.  When Culhane poked his head inside the greenhouse during sunlit hours the temperature was sweltering and uncomfortably hot; well over 40 C.  It was clear that a simple greenhouse structure like those already existing in the Hinku valley could provide much of the thermal gain necessary to keep the digester at the proper operating temperature if the digester were well insulated and the heat was supplemented by hot water feeding (A note to the thermodynamicists in the audience: a well insulated digester wouldn't experience much heat loss or heat gain due to the ambient temperature of the air in the surrounding greenhouse; the function of the greenhouse would be to prevent heat losses by maintaining a temperature greater than that of the digester above the digester. This would inhibit heat from flowing up into the greenhouse. Hot water feeding would do the main heating of the slurry in the digester).


Families in the Hinku Valley and elsewhere in Nepal's highlands could replicate what is being done in China where the fertilizer produced by the biodigester flows into the greenhouse soil, radically improving its productive capacity. As this is occuring, CO2 is expected to build up at the bottom of the greenhouse through bacterial action in the soil, helping to buffer the temperature; one can also burn a portion of the biogas produced directly into the greenhouse  to not only keep it warm at night and during cloudy times but to increase the CO2 levels in the entire greenhouse therebye causing an additional "greenhouse effect" -- the same one now threatening our global climate whereby carbon dioxide acts as a heat trapping gas.  The elevated CO2 levels would also accelerate plant growth.  In all of these ways a combination of biodigester and greenhouse makes a very powerful solution set for improving the quality of life and the quality of food for people in the highlands of Nepal.

I visited the labs at Tribhuvan university  and saw not only the same  Puxin biogas system that we had installed in a girls school on the island of Palawan in the Philippines the previous month,  but a bunch of improved cookstove designs and gasification designs.  I also met students working on biogas and home made wind power solutions.  They are now part of our Solar CITIES biogas innoventors and practioners group on facebook and I have been corresponding with them since getting back to Germany.  The consensus from our conversations has been that high altitude biogas will be fairly simple to achieve, but it needs targeted investment and a dedication to proving the model.


Families in the Hinku Valley and elsewhere in Nepal's highlands could replicate what is being done in China where the fertilizer produced by the biodigester flows into the greenhouse soil, radically improving its productive capacity. As this is occurring, CO2 is expected to build up at the bottom of the greenhouse through bacterial action in the soil, helping to buffer the temperature; one can also burn a portion of the biogas produced directly into the greenhouse  to not only keep it warm at night and during cloudy times but to increase the CO2 levels in the entire greenhouse therebye causing an additional "greenhouse effect" -- the same one now threatening our global climate whereby carbon dioxide acts as a heat trapping gas.  The elevated CO2 levels would also accelerate plant growth.  In all of these ways a combination of biodigester and greenhouse makes a very powerful solution set for improving the quality of life and the quality of food for people in the highlands of Nepal.

I visited the labs at Tribhuvan university  and saw not only the same  Puxin biogas system that we had installed in a girls school on the island of Palawan in the Philippines the previous month,  but a bunch of improved cookstove designs and gasification designs.  I also met students working on biogas and home made wind power solutions.  They are now part of our Solar CITIES biogas innoventors and practioners group on facebook and I have been corresponding with them since getting back to Germany.  The consensus from our conversations has been that high altitude biogas will be fairly simple to achieve, but it needs targeted investment and a dedication to proving the model.

post heat is already well known in the Khumbu where potato growing families have built above ground composting toilets next to the houses and lodges that use rhododendron leaves with the human fecal material to create high temperatures that turn both aerobically into high quality fertilizer.  In some cases the heat is also exploited to heat animal sheds or the homes themselves. This practice is unknown to most people in the Hinku valley where potatoes are not grown and where toilets are generally pit latrines located far from the home (usually next to rivers, which creates the possibility of unsanitary conditions and ground water contamination). 

Anrita Sherpa and Culhane spent time in Khote and Khare discussing the advantages of compost toilets and shared their experiences in the Khumbu and around the world with composting toilets.  Since compost heat has already been demonstrated to be effective for biogas systems by the BSP in high altitude situations it is just a matter of integrating the various systems that are already found in the region into a best practice model that will replicate. 

Once compost systems and cooking systems and greenhouses are all connected there should be plenty of heat for a robust biogas solution.  Aluminum-lye reactions can still play a role but they will become less and less necessary.  Ultimately the chief use for aluminum may be for low-grade lighting and peripheral electronics charging until it becomes profitable to take the aluminum to an actual recycling center.

Culhane has discovered that it is worth carrying small bottles of crystalized Sodium Hydroxide (NaOH) salts, purchased as drain cleaner, wherever he goes to power his "Solar CITIES tab torch" and suspects that once people catch on to how easy it is to get some light from aluminum, they will keep on hand bottles of NaOH crystals or liquid drain cleaning preparations, much as we do under most kitchen sinks in developed countries, or will prepare enough KOH so that they can get instant light when there are no batteries or instant heat and hydrogen when needed.  Since both NaOH and KOH are used in soap making they are hardly rare or exotic chemicals, no matter what their origin, and most societies will  have some around or know how to make them so that they can be used for other purposes like heat, light and electricity and hydrogen formation.

Summing it up on the way to the summit

Our trip to the Hinku valley, like the one to the Khumbu the year before, gives us great confidence that we can solve the energy and health and ecological problems currently plaguing the high altitude communities of Nepal.

When I visited Prof. Dr. Tri Ratna Bajracharya at Tribhuvan University at the end of this expedition he was kind enough to give me the "Proceedings of the Third International Conference on Addressing Climate Change for Sustainable Development through Up-Scaling  Renewable Energy Technologies" of which he was one of the editors.

This conference, held from October 12-14, 2011 in Kathmandu, covered the following topic:


29.  Bimethanantion of Organic Waste under Psychrophilic Conditions

These data support our summary of opportunities for the Hinku Valley.

Pradhan, Sharma et al.  (27)  say "Hydrogen is an important intermediate product in anaerobic digestion. Therefore, if the final step of methnogenesis were blocked by inhibiting methanogens, only acidogens would be left to produce hydrogen, carbon dioxide and volatile acids...(p. 143) Hawkes et. al (2007) has reported on two stage hydrogen-methane process and found most of the two stage process has a higher total efficiency in terms of waste retreatment and energy recovery than a traditional one stage process."   While their work seeks to inhibit methane production to harvest the hydrogen, our proposal is to use hydrogen produced through ash-lye and scrap aluminum reactions to enhance methane production while liberating significant quantities of heat ( 31 kilojoules per gram of aluminum released as heat during the reaction) 

Jha, Bhattari and Liu  (29) point out the potential for using bacteria acclimatized to psychrophilic conditions; in our expedition in 2011 to Mt. Everest Base Camp Culhane brought back active psychrophilic methanogens that were making methane under the ice in mud wallows and ponds along the Khumbu trail and, by feeding them organic waste, proved that they were capable of making good yields of biogas.  These bacteria are available all over the high Himalaya regions. 

They write, "Most of the psychrophilic studies relate to biomethanantion by low temperature acclimatized mesophiles (psychrotrophs; not true psychrophiles) (Kashyap et al. 2003).  As a result the majority of remedies proposed in the literature to enchance biogas production are aimed at  increasing  the digestor temperature to mesophilc range such as the use of the gas produced for preparation of feed slurry, integration of a green house, construction of a system below buildings (heat transfer from the barn) and use of excess gas to heat up the digester to maintain higher digesester temperature (Sutter et al. 1987; Zeeman et al, 1988). However, these techniques suffer from techno-economical constraints (Kashyap et al. 2003). The energy required to heat the process makes it uneconomical in temperate climates".

Nonetheless, Culhane and Katey Walter Anthony, on the first Blackstone Ranch/National Geographic Innovation Challenge grants in 2010, demonstrated the effectiveness of biodigestors inoculated with true psychrophilic bacteria obtained from thermokarst lakes in Alaska. Their research further suggested that greater efficiencies could be obtained from a mix of true psychrophiles and psychrotrophic mesophiles, taking advantage of the fact that the water in the digester tends to settle into distinct thermoclines so that slurry between 10 and 20 C is found at the bottom of the digester while slurry between 20 and 40 C can be found at the top of the digestor.  With proper design (the use of vertical surface in the tank for biofilm formation) psychrophiles can coexist with mesophiles. The psychrophiles inhabit the bottom regions of the tank and the mesophiles the upper regions.  The data of Walter Anthony and her group showed greater production of biogas from a mixed tank kept in a room of ambient temperature 25 C than either population considered alone.

Jha, Bhattari and Liu corroborate these observations in their papaer stating "with the extension of retention time and diminishing loading rate psychrophilic anaerobic digesters can successfully degrade organic matter for reasonable biogas production (Lettings et al., 2000; Lettomaga et al, 2001; Sutter and Wellinger, 1985)... Yu and Gu (1996( reported that psychrophilic anaerobic digestion is stable and is as mesophilic or thermophilic digestion processes. A reduction in pathrogenic micro organisms by psychrophilic anaerobic digestion was also observed (cote et al, 2006)." 

These data have fit nicely with the proposal Culhane has made for Hinku and Khumbu development, suggesting that psychrophilic bacteria be obtained from the Khumbu and Hinku Valley glacial lakes, combined in a modified digester with yak dung and human fecal material derived mesophiles and the system be used to degrade all organic wastes, from food scraps and toilets, to produce  energy for heating water and space that can replace firewood and fossil fuels while creating a valuable fertilizer and reducing pathogens as the preferred solution for waste water treatment.  With the addition of hydrogen thermal energy generation and hydrogen feeding of the digesters taking advantage of the aluminum and ash waste in the region, supplemented by compost and greenhouse and solar heat, 
the challenge of stopping both indoor air pollution and deforestation as well as greenhouse gas emission should be solved.

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