James Kamm

University of Toledo,

Toledo, OH 43606,

E-mail: jkamm@utnet. utoledo. edu

Abstract

Directly burnable biomass to be used primarily in steam boilers for power production has been researched and demonstrated in a variety of projects in the United states. The biomass typically comes from wood wastes, such as tree trimmings or the byproducts of lumber production, or from a cash crop, grown by farmers. Of this latter group, the main emphasis has been utilizing corn stover, or a prairie grass called switchgrass, or using tree seedlings such as willow. In this article, I propose an alternative to these energy crops that consists of several different herbaceous plants with the one consistent prop­erty that they annually generate an appreciable bulk of dried-down burnable mass. The fact that they are a set of plants (nine are offered as candidates) gives this energy crop a great deal of flexibility as far as growing conditions and annual harvest time line. Their predicted yield is impressive and leads to speculation that they can be economically feasible.

Index Entries: Biomass; biofuel; energy crop; sclerified stalked plants; stiff stalked plants.

Introduction

The prospect of biomass as a fuel source is an alluring one. In the first place, it is geopolitically simple; most countries desiring to utilize it can provide their own biomass. In addition, many forms of biomass-to-energy conversions are CO2 friendly, adding no net CO2 to the atmosphere or at least no additional CO2 other than would have naturally taken place. Prob­ably the most exciting aspect of biomass fuels is that they are replaceable; there is no doomsday worry about using up all of EartMs resources. Indeed, some types of biomass are not only replaceable but also renewable; they are or can be created at the same rate that they are used. [4]

For all of the advantages of biomass fuel sources, there are two dis­tinct drawbacks. First, biofuels do not economically compete with conven­tional (oil, gas, coal) fuels. It costs more to generate electricity from biomass compared to coal, and it costs more to power automobiles using biomass fuels compared to gasoline. Second, and probably more important, the sources of biomass are quite diffuse and may not be available in sufficient quantities to make a national impact as an energy use. Biomass is defined as organic material from animals, such as manure, or plants such as trees, grasses, and agricultural crops. Common examples are sawdust as a byproduct of milling wood, rice husks as a byproduct of food production, and pallet and wood crate discards. Ohio claims to produce <1% of its electricity with biomass, and it does it with "forest wastes, such as tops and limbs, and wood wastes, such as sawdust, chips, barks, and edgings" (1). Most of this electrical generation is done within the wood-manufacturing industry (2) and is primarily used internally by the company that gener­ates it.

Plant biomass can also come from "energy crops." Energy crops are "crops developed and grown specifically for fuel. These crops are selected to be fast growing, drought and pest resistant and readily harvested to allow competitive prices when used as fuel" (3). The prospect that farmers will use portions of their vast acreage to produce a material that can be used for fuel seems to have a ring of creditability to it. Whether the power indus­try can pay the farmers enough to turn their heads away from the familiar markets of soybean, wheat, and corn is another issue. Farmers can provide the quantity of material to make biofuel a significant factor in the energy source equation.

Energy crops, or biofuel feedstocks, "under development in the US include hybrid poplar, willow, switchgrass, and eucalyptus" (3). Indeed, prospective energy crops appear to come from both ends of the spectrum of the plant kingdom—monocot herbaceous plants, on the one hand, to more sophisticated hardwood trees, on the other. Switchgrass is a prairie grass (monocot) that grows favorably in the plains states and southwestern states. It dries down to give a burnable product, and the crop has benefited from significant amounts of research performed in states such as Iowa (4), Wisconsin, and Texas and from the Department of Energy through Oak Ridge National Laboratory. On the other hand, willow is a tree, a woody plant whose trunk has annular rings such that it adds woody matter annu­ally to its stem. It appears to be the favored energy crop under investigation in East Coast states, particularly New York where coburning with coal has produced some electricity (5). Both of these energy crops have their propo­nents, both have been the subject of a considerable amount of research and demonstration over the past 10-15 yr, and both are looking more and more promising.

The intent of this article is to introduce another type of plant into the energy crop mix. Of this new type, I suggest nine specific species. These species come from the center of the plant kingdom, between monocots (grasses) and woody plants. All are herbaceous, either annual or perennial. The one common characteristic to all is that their stems die off annually and dry down to give a brittle stiff and relatively hard skeleton. These "remains" of the plant consist primarily of organic carbon-rich compounds and become a source of energy (fuel). Herein, they are referred to as stiff stalked plants (SSPs).

Before introducing and discussing these plants on an individual basis, and in order to understand the significance of the measurements made on and the comments made about each, some consideration should be given to plant botany as it relates to the characteristics of a good energy crop. Plant botany or physiology takes on a completely different thrust when viewed from the perspective of using the dead and dried stem for the ulti­mate purpose. A plant skeleton is really much different, and much simpler, than its living counterpart.