Thanks for an informative article on an important subject that needs more attention.

You may be aware that China has been a leader in use of animal manure for energy. In 1998 I visited a farm complex outside of Shanghai that collected manure, manually by one man in tall boots and a shovel, from several thousand dairy cows and digested the manure in several large stainless steel tanks. The generated biogas was tapped off the top of the tanks and fed to a nearby town that used the gas for cooking in homes and restaurants, replacing coal as the fuel. I have pictures of the tanks and both applications. The dry residue was sold as plant fertilizer, mostly to the Netherlands for growing tulips, and the small amount of liquid leftover was sprayed on the farm's fields as fertilizer. I was impressed and briefed DOE colleagues about this on my return.

Dr. Allan R. Hoffman
Senior Analyst
Office of Energy Efficiency & Renewable Energy
U.S. Department of Energy

An opportunity which you neglected to mention is that the raw biogas produced in anaerobic digestion plants could be upgraded into pure biomethane and the used to replace natural gas in applications requiring a high quality gas grade.

In Europe biomethane produced from animal manure is already being used as a vehicle fuel - either injected into the natural gas grid (allowing withdrawal of a similar volume of 'green' gas from the grid to a vehicle refueling station at another location) or via direct delivery to a vehicle refilling station. Projects have also started in various locations outside Europe (including the USA).

Since society has a need to replace vehicle fuels from fossil sources with fuels from renewable sources one should not overlook the great potentials offered via biomethane. Renewable electricity can be produced in many different ways from sources less well suited for supply of vehicle fuels (wind power, wave power, tidal power, PV power, geothermic power etc).

In Sweden, more than 50 % of the methane gas used to fuel a more than 13,000 vehicles (12,000 LD vehicles, 800 HD buses, and 300 HD trucks) consists of biomethane. Animal manure is one of the most important feedstocks (also including all kinds of biodegradable municipal waste, agricultural waste, and sewage sludge) used for biomethane produced via anaerobic digestion.

In the future biomethane will also be produced via gasification of cellulosic forest industry waste, and methanation of the produced syngas. The technology has already been proven with exceptionally high overall energy conversion efficiency, and the Gobigas project is now underway in Gothenburg, Sweden, aiming for start-up of the first large-scale facility in 2011. One single plant will supply some 80 million normal cubic metres of pure methane annually - enough to fuel e.g. some 80,000 passenger cars. In Sweden the supply of forest waste would suffice for numerous plants of this size).

Peter Boisen
Sweden

This type of technology, taking waste and turning it into energy, gives us one of the best types of renewable energy. We solve two problems at once. This is much more valuable than growing corn to make ethanol, for example.

Jim Colleran
Retired

Electricity generation using animal manure has been on-going in Marine County, Ca for some 2 decades now. It works, costs are predictable, and the process is both scalable and amenable to any climate. All one needs is a lot of 'manure' in one place and an electrical distribution grid that will accommodate the power generated.

Large animal farms (cows, horses, pigs, chickens, turkeys) are potential users. Each 'source' of manure has somewhat different issues to manage though. This is yet another way to capture solar energy--from photosynthesis-and use it in several steps to our benefit.

I feel that ALL Operations with large concentrations of these animals (dairy's, feedlots, etc) should be REQUIRED to manage this manure by digesting and generating electrical power. It will significantly lower the negative impact that high numbers of large animals have on the surrounding environment. The power so generated SHOULD be 'bought' at the highest incremental value since it has such a positive environmental impact.

We, The People, have too long ignored the degradation of the environment, both water pollution and 'greenhouse gas emissions', caused by these animal farms, and this is one way to mitigate it AND improve profitability of those Operations.

Keith Bowers
Principal
B&B Consulting

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