Biogas Basics
Brian Luedtke
blued692@uwsp.edu


With fermentation technology known about for hundreds, if not thousands of years, we are just now recognizing the potential of biogas. "Enough biogas could be generated in Wisconsin to power about one-third of the state," said Erik Singsaas, Director of Research for the Wisconsin Institute of Sustainable Technology and Associate Professor of Biology at the University of Wisconsin-Stevens Point. In comparison, 60 percent of Wisconsin’s electricity currently comes from coal shipped in from out of state. The remaining 40 percent is made up by nuclear power, natural gas and renewable energies like hydroelectric, wind, solar and biomass gasification.

What is biogas?
Biogas is the result of the conversion of waste products in an oxygen-lacking (anaerobic) environment to a gas comprised mainly of carbon dioxide and methane with small, varying amounts of water vapor, hydrogen sulfide and possibly ammonia. This process is commonly referred to as anaerobic digestion. Biogas is very similar to natural gas in that methane is a major component.
​Organic residues such as food scraps and animal wastes enter the anerobic
digecster, where they are converted to biogas and digestate. The Biogas is
used similarly to natural gas. The digestate can be used as a fertilzer.
Diagram courtesy of StormFisher.com
 
The use of Biogas decreases greenhouse gas emissions by capturing and combusting methane, releasing carbon dioxide instead. According to the U.S. Environmental Protection Agency, methane is roughly 21 times more potent as a greenhouse gas than carbon dioxide.

Across the U.S., commercial waste diversion through anaerobic digestion and composting is becoming a popular practice (catching up with other countries like India, China and parts of Central America and Africa). As an example, San Jose, California will have source-separated organic waste collection which runs on self-produced energy from biogas and sells a finished product, compost and electricity, while collecting a tipping fee. This is the first large scale green energy and municipal solid waste compost facility of its kind in the United States. Several municipalities around the country and world are considering, if not already planning or building, this type of system - renewable energy from organics recycling.

Biogas can be used in several ways.

1. Electricity
A Bloom Energy Server® is a 100 kilo Watt fuel cell which turns natural gas or biogas into electricity through a combustion-free electro-chemical process. The energy Servers® are about the size of one parking space and can be linked in series. That is, connected together to reach a desired output.
Biogas can also be combusted in slightly modified internal combustion engines to generate electricity and heat. The latter can be used to heat air for offices and warehouses or water for greenhouse and dwelling type applications. In fact, the Stevens Point wastewater facility combusted methane generated in their anaerobic digester for electricity generation from the 1940’s to the 1960’s.

2. Fuel
Fair Oaks Farms of Fair Oaks, Indiana has rolled out a fleet of compressed natural gas (CNG) powered milk tanker trucks. The trucks will run on biogas created at the Fair Oaks Dairy anaerobic digester, which is capable of processing manure from 10,500 cows. Their switch alone will reduce their diesel fuel consumption by more than 1.5 million gallons per year.

3. Fertilizer
Aside from producing biogas, anaerobic digestion results in a liquid, known as supernatant, and sludge. The liquid is often used as a fertilizer, while the sludge is commonly composted or dried and pellitized. Both can also be done, then used as a soil amendment or potting mix.

Wisconsin and biogas, astory of destiny

Wisconsin, host of the 11th Annual Biocycle Conference on renewable energy, is among the leaders in the biogas realm. Anaerobic digesters are appearing at feedlots and dairies across the state. Even Ben Brancel, Secretary of the Wisconsin Department of Agriculture, Trade and Consumer Protection, has voiced support for biogas and an increase in renewable energy production in the state.

Bloom Energy Server in use at Ebay headquarters in San Jose.
Photo courtesy of jbtimes.com
 


Biogas is not something that is simply casually passed or played off as a squeaky chair, shoe or weird new shampoo. Biogas is a real fuel, created by responsibly managing real waste. Whether whey from cheese production, manure from cattle, brewery mash or food scraps, the end product is locally usable and producible with environmental benefits at all scales.