Introduction

Today, experience of the use of combustion motors to produce electricity from biogas is extensive; this can be regarded as a proven standard technology. Over 4,000 biogas plants with internal combustion motors are in operation in Germany. - [1]
1 cu m of biogas yields 1.7kWh of electricity (1.7kWhel)
Many new studies come to the conclusion that biogas power plants are not commercially viable without subsidies or guaranteed high prices (~0,20US$) for the produced outputs. In Germany and other industrialised countries, only guaranteed feed-in tariffs have led to a breakthrough. Almost all well-known biogas power plants in developing countries depend on financial support from a third international party. -[2]

Costs

$2480/kWel minimum installed capitalization cost with under 1 cent O&M costs per kWhr, California - [3]. Baseline comparison: $1/W for coal power capitalization cost.
Simple agricultural plant could cost as low as $3,500 per electrical kW installed - [4]
$660 per cow installed cost - 2 kWhr, or $7900 per continuous kW - [5]
- Also shows 0.2kW/cow continuous production
Biogas production costs are comparable to the cost of natural gas, or about $7/1000 cu ft - [6]

1/2kWel average production system - only microscale biogas electric system in USA - [7]

As Becky Larson, a bio-waste engineer at the University of Wisconsin in Madison points out: “We’re at the cusp of finding a way to make these biogas energy systems profitable,” noting that she expects the biogas market to be pushed along by the continuing emphasis on sustainability; high costs of competing energies; and concern over reduction of greenhouse gas emissions. - [8]
Suppliers - [9]
PDF including build - http://www.biog.as/puxin.pdf