Trillium FiberFuels has evaluated feedstocks in the Pacific
Northwest region and paired each with the appropriate conversion technology.
Feedstocks: The Oregon Department of Energy
created a report in 2000 that outlines the cellulosic resources for the state.
Each of these streams has a set of attributes associated with cost, variability,
availability, and geographic distribution. Summarizing our findings for each
material:
- Forest residues including scrap wood, sawdust, and thinnings. While
there are substantial amounts of these materials, there are significant
issues. From a conversion point of view, softwood residues are very high
in lignin. This makes enzymatic conversion very difficult with most pretreatments,
except possibly a solvent-based approach. Thermochemical processing is
possible, but not a preferred technology path for us due to scale and
toxic co-product issues. Much of the perceived available material is also
too expensive to remove economically. Finally, policy and societal acceptance
of the removal of thinnings for fire reduction reasons are still open
issues.
- Agricultural residues, especially straw. From our analysis, this stream
came out on top. It is low in lignin and hence more susceptible to enzymatic
processing. It is local for us in the form of ryegrass straw and yet the
class of materials (straws) have worldwide potential. Wheat and rice straws
are present in our region and represent massive feedstocks across the
globe. Another smaller plus is that straw is already partially size reduced
compared to woody feedstocks. This lower the energy input required for
processing. We have worked with the USDA Research Station in Corvallis
to utilize their GIS database to identify feedstock distribution and optimal
biorefinery siting.
- Paper mill sludge is a small feedstock that may be used to supplement
a larger stream. In the past year, two of the mills in the region have
closed and the industry is struggling. This material is best viewed as
an opportunistic boost.
- Mixed paper waste is better used for recycling into paper - a higher
value material than ethanol.
- Municipal Solid Waste (MSW) has the desirable feature of being a true
"negative cost" feedstock. People will pay to have it removed.
The challenge is that it is rather variable in content. Items that are
particularly worrisome are batteries or other materials that would contain
heavy metals that could inhibit the enzymes or yeast. Despite this, it
is being proposed in California by Bluefire. Thermochemical processing
is also possible and proposed by PNNL. Thermochem is not our first choice
for reasons noted above.
- Greenwaste (lawn clippings, etc) is a small but useful feedstock. It
can be a useful supplement, but it very high in water content so hauling
distance must be kept very short.
Based on this work, we have spent significant time studying
the chemistry of straws and developing a process flow to optimize yield. During
this work, we realized that nearly all feedstocks face the issue of xylose
utilization. Technology for xylose utilization has
become the major focus at Trillium.
