Published: September 2004
Petrochemical hydrocarbon sources are finite and many experts suggest that they will become exhausted within decades. In addition, both natural gas and crude oil have recently experienced an upward shift in pricing trends. The use of bio-based sources such as plant/crop wastes provides inputs that are renewable and creates the opportunity for a transition to a more sustainable economy. There is also the hope that in the near future, cellulosic plant/crop wastes will become economically competitive with petrochemical feedstocks. There are numerous challenges, both technical and infrastructure related, associated with commercializing lignocellulosics as feedstocks for chemicals. While large quantities of various crop wastes go unused throughout the world, these lignocellulosic materials are difficult to efficiently convert into chemical products due to their complex polymeric structures. A multi-disciplinary approach that couples biotechnology and chemistry with process engineering is necessary in order to achieve efficient commercial processes. In addition to the technical challenges of commercializing this technology, there are also large infrastructure barriers. These barriers are associated with the development of new agricultural infrastructure for the collection and storage of crop wastes. An integrated feedstock supply system must be developed that can supply the feedstock needs in a sustainable fashion at a reasonable cost. Infrastructure issues could be as important as the technical issues when considering overall production costs.
In this report, PEP presents process designs and associated cost estimates for the production of two chemicals, ethanol and lactic acid, from agricultural wastes. Technology development is in the semi-commercial stage in North America, Europe and Japan for economically producing fuel grade ethanol from a crop waste such as corn stover, wheat straw or rice straw. Process economics are also estimated for producing lactic acid from corn stover, a technology that is more recently under development. Ultimately, the best process economics for the use of these feedstocks could come through the development of the "biorefinery," a concept also discussed in this report. For lignocellulosic biomass to be economically viable as an ethanol feedstock, the Department of Energy has chosen a target ethanol selling price of $1.07 per gallon (28¢ per liter) as a goal for 2010. Our PEP analysis indicates that more progress must be made in biomass conversion technology to meet that goal. Our PEP analysis of lactic acid production from corn stover indicates a good potential for manufacturing the chemical profitably at prices significantly below current market prices. Corn stover has a good potential as a lactic acid feedstock after conversion technology has been demonstrated at the commercial scale for producing ethanol. For those in the chemical industry, this report will be useful for the comparative economics it provides, as well as for its extensive review of ongoing research related to biomass conversion technologies. The report reviews and analyzes more than 200 recent patents and articles related to biomass conversion. The report's review of biomass availability around the world will also be useful for those exploring this field.