Conversion Technologies: There are several methods for converting cellulose to ethanol and the best approach varies depending on the feedstock chosen. The main categories are thermochemical, acid catalysis plus fermentation, and enzymatic catalysis plus fermentation.

Thermochemical conversion involves taking the biomass and heating in the absence of or partial absence of oxygen. With no oxygen, the biomass changes to an oily substance that can be further refined. This is called pyrolysis. If there is partial oxygen present, the biomass changes into carbon monoxide (CO) and hydrogen (H2). Why would you want to do this? These products, which are called synthesis gas (or syngas), are readily transformed into other compounds using catalytic reactors. Trillium has not chosen this route because the process also produces a large number of undesirable byproducts, some of which are carcinogenic. In some reports we have seen, pyrolysis oil has more benzene (a known carcinogen) than petroleum based gasoline. So, despite the feedstock being green, we don't give these processes high marks for sustainability. Another issue is that the technology appears to tend toward large, centralized installations. We believe this works a bit against the grain of the distributed opportunity available and also poses a large capital barrier.

Acid catalysis was discovered about 100 years ago and fermentation long before that. The main thing that is new is the high price of petroleum! There are several versions of this process all striving to be cost effective. Most (if not all) suffer from issues related to the degradation of sugars into compounds which inhibit the yeast during fermentation.

Another form of catalysis uses enzymes, which are natures own catalysts. These compounds, created by various organisms such as yeast, bacteria, and fungi, are used in nature to break down and recycle woody (cellulosic) materials. They are elegant in form and function. They also tend to be rather expensive due to the processes required to extract them from cultures of the microorganisms. Unlike the acid, they also tend to be rather specific and may only work on a single class of feedstock. Another issue related to the use of enzymes is the interaction with lignin. Lignin is a polymeric material present in the plant that acts as the "glue" to bind the structural components of the plant together. During the processing of the biomass, the lignin may bind with the enzymes and render them inactive. The more lignin present, the bigger the problem. Softwoods, especially our own Douglas Fir, are very high in lignin and make enzymatic processing very challenging. One successful technique is to dissolve the lignin with a solvent such ethanol. A company in British Columbia is focused on this method (Lignol). Feedstocks with lower lignin content such as straws are a good fit for enzymatic processes. We feel that the best opportunity in our region for biorefineries is this combination of straws and enzymatic conversion. There are still significant challenges in pretreatment, water usage, and more, but the potential is strong.

One challenge fit nearly all feedstocks face is the utilization of pentose sugars. Starches and refined sugars are hexoses which means the backbone of the sugar contains six carbon atoms. Most of the familiar sugars such as glucose, and fructose are in this category. Nearly all biomass also includes sugars based on five carbon atoms, especially xylose. Pure xylose looks and tastes like ordinary sugar. However, typical yeasts do not ferment it to ethanol to any appreciable degree. Since the utilization of xylose represents a 20-40% increase in ethanol yield per ton of biomass, it is imperative to ferment this material to achieve good economy in most cases. Technology for xylose utilization is now the major focus at Trillium.