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Supply of bioenergy and fossil fuels
by David Bransby

Bioenergy offers opportunities
 to alleviate problems related
 to supply of fossil energy

Bioenergy is energy in the form of liquid fuels (e.g. ethanol and biodiesel), heat and electricity produced from biomass such as wood, hay, crop and forest residues, and animal waste. On the other hand, fossil energy is produced from fossil fuels (oil, coal and natural gas) and their derivatives. It includes electricity and liquid fuels like gasoline and propane. 

While most of us recognize that oil and coal are fossil fuels, many people do not really consider natural gas to fall into this category. Maybe this is because the term ‘natural gas’ seems to imply that it is clean and renewable. Although natural gas is the cleanest of the fossil fuels, it is important to recognize that it is just as much a fossil fuel as oil and coal.

Most of the energy we use today is derived from fossil fuels. However, problems related to fossil energy are serious, and are increasing. While bioenergy also has some disadvantages, it offers some distinct advantages over fossil energy. The focus of this article is on advantages and disadvantages related to the supply of these two sources of energy.

Biomass is currently being co-fired with coal on a small scale at Alabama Power’s Gadsden plant. The higher cost of biomass compared to coal is still an obstacle to widespread use of this technology, but potential solutions to this problem are currently under investigation.

National Supply

Fossil fuels are finite. This means that sooner or later we are going to run out of them. Depletion of oil and natural gas is expected to occur before depletion of coal. While it might be a long time before complete depletion of these resources occurs, the impact of their increased use will be realized much earlier.

Economists predict sharp increases in the price of fossil fuels when demand becomes equal to supply. Several credible sources estimate that we are already at this point with regard to oil, or very close to it. Although coal reserves are expected to last longer, increased demand for coal from China, due to its rapidly expanding economy, has recently contributed to a substantial increase in price. The sharp hike in the price of natural gas and propane speaks for itself, and threatens the economic viability of many domestic industries that are considering moving off shore due to lower natural gas prices in other countries. 

Another major disadvantage related to the supply of fossil energy is that the U.S. now imports over 60% of its oil. This poses a serious threat to national security and stimulates conflict among nations on a global scale, as evidenced by our military presence in the Middle East. It also contributes substantially to our negative balance of payments at the national level.

In contrast to fossil fuels, bioenergy is renewable. In other words, the energy in our vegetation, crops and other biomass resources is replenished by plant growth every year. Estimates of how much energy is trapped annually on a global scale by plants and microorganisms through photosynthesis vary widely, from three to eight times the amount of energy used by our global human population. However, even if the most conservative end of this scale is considered, it should be a while before demand exceeds supply. Clearly, this is a major advantage over fossil fuels. The challenge, of course, is how to collect and convert the energy contained in biomass into an economically competitive and usable form. 

Bioenergy is also literally home grown. Therefore, it does not pose the national security threat or negative impact on our balance of payments that are related to imported oil. Furthermore, it offers the potential of new local markets for agriculture, and a related stimulus for depressed rural economies.

State Supply

While Alabama enjoys a good supply of natural gas, we import https://www.alafarmnews.com/files/0305archive/almost all our gasoline and related products, and over 60% of our coal. as in most of the southeast, about 70% of our electricity is generated from burning coal, the balance coming mainly from hydro and nuclear sources. 

Ten years ago all the coal needed to generate electricity in Alabama was mined inside the state, but we now import over 18 million tons of coal each year, mainly from Wyoming. The reason for this is that coal from Alabama is high in sulfur and leads to high levels of sulfur dioxide emissions when it is burned. These emissions negatively impact our environment and are subject to controls imposed by the EPA.

Coal from Wyoming is low in sulfur. Therefore, using it instead of local coal to generate electricity reduces emissions of sulfur dioxide. However, this also results in over $500 million leaving the state every year to buy coal, and it is well recognized that our state government cannot really afford that.

A definite advantage of fossil fuels is that they have a high energy density compared to biomass. For example, bituminous coal contains about 700,000 British thermal units (Btu) per cubic foot, while wood chips usually contain no more than 100,000 Btu per cubic foot. This makes fossil fuels a lot cheaper to transport, thus facilitating longer hauling distances, and processing in large refineries. The low energy densities of biomass make it necessary to locate bioenergy processing facilities close to the source of the raw material in order to minimize transport costs. However, the many pulp mills across the Southeast provide evidence that this is entirely feasible. 

Potential Role of Bioenergy

Southern Company Services and Alabama Power, with support from Southern Research Institute and Auburn University, have demon-strated that it is technically feasible to co-fire up to 10% biomass with coal to produce electricity from existing coal fired power plants. Capital investment required to do this is relatively low compared to that needed to build totally new power plants, and there are several related advantages. One of these is that biomass has an even lower sulfur content than coal from Wyoming.

If all coal fired power plants in Alabama co-fired 10% biomass, and this biomass replaced imported coal, $72 million would be kept from leaving the state each year, and a new biomass market of $234 million per year would be created. At the local level, if the Alabama Power coal fired electricity plant at Demopolis in the impoverished Black Belt region of the state co-fired 10% biomass with coal, it would require 317,000 tons of biomass per year and 63,400 acres. At a price of $50/ton this would create a new market of $15.9 million per year which would certainly stimulate the local economy. Similar figures are provided for other power plants in the state in Table 1, below.

So if the benefits of co-firing biomass with coal to produce electricity in Alabama are so obvious, why is co-firing not being applied on a large commercial scale? It is generally not known that co-firing is actually being conducted on a continuing basis, but on a small scale at Alabama Power’s Plant Gadsden. The higher cost of biomass compared to coal remains an obstacle to widespread use of this technology, but potential solutions to this problem are currently under investigation. Further information on this issue will be provided in a future article on bioenergy. 

Table 1. Selected Coal fired power plants in Alabama, their locations,
 and their biomass co-firing needs and potential at 10% of coal input.

Plant Name Capacity Location Biomass needs
Acres needed Biomass Value
Barry 750 MW Mobile 467,000 93,400 $23.4 million
Gadsden 70 MW Gadsden 44,000 8,733 $2.2 million
Gaston 1,020 MW Wilsonville 635,000 127,000 $31.8 million
Green 509 MW Demopolis 317,000 63,400 $15.9 million
Gorgas 557 MW Walker Co 347,000 69,000 $17.4 million
Miller 1,000 MW West Jefferson 624,000 124,000 $31.2 million
Totals 2,434,000 485,533 $121.9 million



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Date Last Updated January, 2006