Page 353 - Solid Waste Analysis and Minimization a Systems Approach

IMPLEMENTATION AND APPROACH 331

Biomass can be converted into a gas by heating it under pressure and without oxygen
in a gasifier. Manure too can be converted using a digester. The gas can then be burned
to produce heat, steam, or electricity.
Other biogas applications are still in development, but show great potential. One
promising technology is direct combustion in an advanced gas turbine to run a gener-
ator and produce electricity. This process is twice as efficient as simply burning raw
biomass to produce electricity from steam. Researchers are also developing small,
high-speed generators to run on biogas. These microturbines have no more than three
moving parts and generate as little as 30 kW, which could power a medium-sized farm.
Several companies are also considering converting gasified biomass into ethanol as a
less expensive alternative to fermentation.
Alternatively, biogas can be processed into hydrogen or methanol, which can then
be chemically converted to electricity in a highly efficient fuel cell. Fuel cells can be
large enough to power an entire farm or small enough to power a car or tractor.
An innovative experiment in Missouri provides one example of the possibilities.
Corn is used to produce ethanol, and the waste from the process is fed to cows for
dairy production. Cow manure fertilizes the corn and is also run through a digester to
produce biogas. A fuel cell efficiently converts the biogas into electricity to run the
operation. The end products are ethanol, electricity, and milk. All the waste products
are used within the project to lower costs.

22.6 Implementation and Approach

To implement waste minimization strategies several options are available. The federal,
state, and local governments offer numerous support programs. In addition, the orga-
nization’s current waste hauler may have options to reduce solid waste or divert it from
landfills, such as recycling and compost programs.
Crops grown for energy could be produced in large quantities, just as food crops are.
While corn is currently the most widely used energy crop, native trees and grasses are
likely to become the most popular in the future. These perennial crops require less
maintenance and fewer inputs than do annual row crops, so they are cheaper and more
sustainable to produce. Following is a list of the three commonly used crops to gener-
ate energy:

■ Grasses—Switch grass appears to be the most promising herbaceous energy crop.
It produces high yields and can be harvested annually for several years before
replanting. Other native varieties that grow quickly, such as big bluestem, reed
canarygrass, and wheat grass, could also be profitable.
■ Trees—Some fast-growing trees make excellent energy crops, since they grow back
repeatedly after being cut off close to the ground. These short-rotation woody crops
can grow to 40 ft in less than 8 years and can be harvested for 10 to 20 years before