Biomass is plant or animal matter. Using biomass (or fuels or wastes derived from biomass) as a source of energy entails burning it to yield heat that can then drive engines or generate electricity. The energy in biomass is chemical in nature; it does not suffer from the problem of intermittence that is inherent to wind and solar resources. In this respect, biomass more nearly resembles fossil fuels than it does other renewables. Indeed, geologists tell us that fossil fuels are simply fossilized biomass.
For most of recorded history, biomass was mankind's principal energy source, mainly in the form of wood used for cooking and heating and as foods to "fuel" human labor and beasts of burden. With the industrial revolution, fossil fuels captured this dominant role. Today biomass still accounts for 15% of worldwide primary energy consumption, but, significantly, the fraction is much higher in developing nations than in developed ones.
Perhaps the most important factor to remember about biomass' potential role in the energy sector is that, again unlike most renewables, stiff competition will always exist for both the biomass and the requisite land resource to grow it. This is often capsulized in the five "f's" of biomass usage: food, feed, fiber, forage, and fuel. Fuel -- growing biomass to burn it -- will normally be the least valuable on this list. Even among wastes derived from biomass, higher value applications may diminish their use as fuel: manures have value as fertilizers; waste paper can be recycled; cottonseed hulls find their way into oil drilling muds, wood chips into landscape mulches, restaurant greases into pet food. Although many specialists have envisioned a role for biomass in which it is grown extensively and solely for fuel (energy crops), it is probable that this can only happen with at least some valued dual use or co-product derived from the crop.
As one of the nation's leading agricultural states and with a large forest industry, Texas is a major biomass producer (see Figure 8). Additionally, the state's very large urban base contributes substantial amounts of biomass-derived wastes. Figure 9 identifies Texas' major production areas and the types of biomass that each generates.
|
| ||
 AGRICULTURE |
 FORESTS |
 URBAN BIOMASS |
|
Harvest Residues |
Logging Residues |
Municipal Solid Waste |
Prime agricultural areas include regions along the Gulf Coast, the central Blackland Prairie, the High Plains of the Panhandle, and delta lands near the mouth of the Rio Grande. Switchgrass, a tall native grass proposed as an energy crop by the Department of Energy (DOE), can be grown in all of these regions, but in the Panhandle only under irrigation. By far, the state's major agricultural process residue is cotton gin trash. Cotton is grown throughout the state, but its production is concentrated in the Panhandle. Other locally abundant agricultural wastes include rice hulls, sugarcane bagasse, and cottonseed hulls. Manures generated throughout the state, but again concentrated in the Panhandle, also form an important resource.
Wastes generated by the forest products industry of East Texas include logging residues left behind after harvest as well as bark, wood chips, and sawdust generated at mills. In general, the wood wastes generated by modern mills are highly utilized; indeed, forest mills are the largest biomass energy users in the nation today, generating more than half of their large energy requirement on-site. Many mills, including currently five in Texas, generate electricity for local use or occasionally for resale to the grid. East Texas also holds potential for the cultivation of woody energy crops, mainly hybrid poplars (cottonwoods) presently being studied by the DOE.
Urban sources of biomass may represent some of the best opportunities for increasing biomass' near-term presence in the energy mix. Wastes that would otherwise be landfilled are a particularly good potential fuel source since the producer is charged a tipping fee for their disposal. Texans landfilled over 20 million tons of refuse in 1993, nearly 75% of which comes from biomass. Methane gas generated and captured at existing landfills or at municipal sewage treatment facilities is another important form of urban bioenergy. A final advantage of these wastes is that their supply is surprisingly reliable, much more so than agricultural commodities that fluctuate annually with the vagaries of markets, weather, and government policy.
Texas is a major biomass producer with a number of very good resources. The variety of plants, animals, residues, and biofuels that fall under the biomass heading is difficult to recount in a short space, but in general, wastes will remain the most important biomass energy sources, with those that currently present a disposal problem having the greatest near-term potential. Energy crops may make longer term contributions to the energy sector and could help farmers and rural communities by establishing new markets for their products.
