Its origins may not exude the sweetest smell, but biogas, which is the product of anaerobic digestion (decomposition without oxygen) of organic matter, such as sewage, animal waste, and municipal solid waste, serves as another energy source that can help offset the use of nonrenewable resources. For the purposes of this chapter, however, we will focus on only two of the largest sources of biogas that are actively being used right now for power generation:
Landfill gas (LFG)
Before we discuss how to make money by investing in biogas, we should quickly address the argument that using landfill gas for energy cannot be considered "green" for two reasons. First, it is suggested that if an energy source emits dioxin (LFG combustion can produce small quantities of dioxins), it's not really green. While we agree with this statement, it could be equally argued that it's still better than coal, and therefore should not be disregarded when discussing alternative forms of power generation.
The second reason is that LFG uses excessive amounts of waste that could otherwise be composted, or never generated to begin with. Certainly producing less waste would be the best bet, environmentally speaking. But as much as we advocate minimizing waste, it would be senseless for green investors to disregard the use of LFG for energy. Whether we like it or not, as a society, we waste a lot. And as our numbers grow, so ...