Biomass energy has been around since ancient time and long before anyone spoke of renewables or alternative energy sources. There was a time when biomass in the form of wood was the primary fuel for heating and cooking around the world. Although, this practice is less widespread today, biomass in general is perceived as an important component of an overall energy policy. However, there are a number of issues associated with certain forms of biomass energy that make them less than ideal solutions.
The primary pros of biomass energy are:
- Widely available and abundant renewable fuel
- Generally low cost
- Low carbon emissions, cleaner than fossil fuels
- Conversion to energy also helps with waste disposal
The primary cons are:
- Biomass energy is energy intensive to produce; in some cases, there is little or no net energy gain
- Land utilization can be considerable and in developing countries can lead to deforestation
- Often requires water to grow, which itself is a scarce resource in parts of the world
- Not totally clean when burned and emits some nitrous oxide, ash, carbon monoxide, and carbon dioxide, as is the case with other fossil fuels
- May compete directly with food production
- Often requires fertilizers, pesticides and herbicides and the energy and resources used and carbon emitted in producing them
- Relatively limited upper capacity for generation
From an overall standpoint some forms of biomass energy would appear to be inappropriate to solve the world's energy problems. These include those methods that compete for other critical resources or take almost as much energy to produce as they generate. The most attractive and efficient options are those that utilize existing waste materials as feedstock, including forestry, agricultural, industrial, and urban waste.
Figure 1 plots solid biomass resources in the US including crop residue, forest and mill residues, and urban wood wastes. Figure 2 plots methane gas generation resources including landfills, animal manure, wastewater treatment, and industrial/commercial organic waste.