BIOTECHNOLOGY AS A KEY DRIVER FOR SUSTAINABLE BIOENERGY PRODUCTION
James McLaren
November, 2005

The idea that bioenergy will become the white knight of the 21^st century is intuitively attractive, and receives much press, across a broad range of political and social agendas. However, on a detailed development level it remains unclear how bioenergy will allow a sustainable platform for continued world economic growth. Einstein said that "problems cannot be solved by the same level of thinking that created them"—solutions to the energy crisis will require different ways of thinking. Shifting from a petro-driven economic base to a bio-based foundation is a significant challenge and success will require more than just "substitution" strategies. There is a need to clearly understand the magnitude of the problem, to accept that new breakthroughs in technology applications are required for any chance of success, and to acknowledge that acceptance of dramatic change is probably required before we can begin to build a more sustainable future.

The problem is straightforward and can be quantified with reasonable accuracy. The world currently utilizes 420 quads/year (quad = 10¹⁵ Btu) and the conservative case projection is that within 30 years the world requirement will be 650 quads/year, largely due to economic development in India and China. While energy demand is growing rapidly, fossil fuel reserves are finite. In addition, if the current global temperature elevation is even partly related to anthropogenic gas emissions then what will happen during the projected massive increase in the use of fossil fuels? A conceptually attractive feature of bioenergy is that carbon dioxide release will be at least neutral due to carbon recycling on a relatively short time-scale.

Currently, bioenergy and bio-based inputs account for less than 5% of all basic inputs to the existing Western economy. While several government-industry initiatives¹ have highlighted the issues and challenges, and some companies have also taken steps to embrace the emerging bio-industry, the pace of change may be too slow. Moving from 5% of inputs to >50% of inputs in less than 20 years is a "moon-shot" type of challenge.

Current Situation
First, it is important to define what "biomass" really means—while there are several meanings being associated with this word, for the purposes of this article biomass is taken as any output from primary production (i.e., plant materials). Traditional biomass can make a useful contribution to bioenergy production and, in recent years, biofuels have been on the leading edge of developments. For example, in 2004, approximately 3.4 billion gallons of ethanol fuel were produced in the US for blending as an oxygenate in gasoline. In this commercial case, the biomass used was largely maize starch (~95%), sorghum starch (~4%), and a small amount of other crop inputs. The application of new production technologies, conventional plant breeding, and early-stage biotechnology traits, have resulted in significant yield increases (at the same level of inputs) in maize. Hence, an increasing volume of grain has been made available for conversion into ethanol with no negative impact on the feed/food segments of the market.²

Lignocellulose biomass has been considered as a potential feedstock for biofuels and other bioenergy³ (e.g., gasification and the generation of electricity as well as steam). Lignocellulose is an abundant material created from solar energy in primary production. Theoretical calculations of conversion to ethanol indicate high potential to generate 25 to 50 billion gallons of ethanol per year. However, lignocellulose is a complex material (lignin, cellulose, pectin) and is not easily converted into biofuel in an economically viable manner. Consequently, progress over more than 20 years of research into conversion technologies has been disappointing in terms of creating an overall viable process for lignocellulose to ethanol.

The current use of biomass (for biofuels) is heavily focused on the development of complex conversion technologies, typically involving a fermentation step. It is only very recently that the first indications of change in the feedstock have appeared. For example, the major maize seed companies have screened their germplasm for hybrids that produce a higher fermentation yield in the dry-mill process.⁴ The results indicate that genetic components for higher ethanol do exist, but these have never been specifically targeted in the past. Major crop plants have been bred (genetically altered via recombination and recurrent selection) primarily for food or feed production, and when was there ever selection pressure to optimize for industrial biofuel traits in wild plants? It would seem there is a huge opportunity to optimize plants for use in bioenergy strategies.

Applications of biotechnology
Biotechnology is a tool that provides an opportunity to design and optimize the feedstock materials, not just the microbial bioconversions in the process. For example, for corn-based ethanol, the particular traits now being explored for improved ethanol production include overall starch production (yield per unit impacts efficiency), starch types (amylose:amylopectin ratios), and compositional interactions. For lignocelluose, much progress has been made on enzymatic conversion of cellulose to ethanol, but the lignin and other components inhibit the overall process.³ Several research groups are now exploring the outcome when lignin biosynthesis is down-regulated—potentially a major breakthrough in moving lignocellulose into the commercial biofuel market.

The preceding comments are focused on ethanol only because it is currently the major biofuel. A very analogous situation exists for biodiesel (methyl esters of plant fatty acids, although recycled cooking oil and animal fats can be used) where the market potential is high but limited by the current overall economics. Strategies that focus on stacking industrial traits, for example, in specifically-designed non-feed soybeans, could open the door to directed design for improvements in subsequent bioenergy use.

There is much written about the future potential of a "hydrogen economy." Nevertheless, it is widely recognized that some inherent technical hurdles may take 10 – 15 years to resolve. Assuming success with those, there remains a need to have an energy source (hydrogen is an energy carrier, not a source) to drive the hydrogen economy. In schools of thought, the current assumption is that fossil fuels (reformulated natural gas) will be the main source, which seems to be a self-defeating achievement. Nuclear power appears to be a more logical choice. However, why would biomass not be a high priority, at least to be explored as a major energy source for a future hydrogen-based system. Research is ongoing into the use of ethanol to power bio-fuels cells.⁵ Biotechnology could also be a valuable tool to explore the possibilities of improved solar energy capture via plants with biosynthesis of material that facilitate energy transfer to hydrogen.

Currently, a number of bio-based products are made from various parts of different crops. The classic example is pulp/paper from lignocellulosic biomass. Others include specialty fibers, adhesives, boards, veggie-candles, crayons, and additives. However, to-date, and with the exception of paper, most have been small niche products due to difficulties in processing and/or product performance issues. Biotechnology really opens several new doors to creating "natural" bio-based products that are viable in contributing to a more sustainable future. For example, 1,3-propandiol (to be used for a polymer that replaces petro-derived polyester) can now be generated from a microbial bioconversion of starch-derived glucose, a process that required 18 genetic-driven changes in the biosynthetic pathway.⁶ A large number of exciting opportunities exist to utilize natural polymers, rather than petro-polymers, for future needs with functional as well as resource advantages. The current well-known example is the spider silk protein that is very light but is stronger than steel. Since it is difficult to harvest spider webs, biotechnology is being used to express the protein in situations where high levels can be produced and harvested with relative ease.

Biotechnology can make a significant difference to the success of a sustainable bio-system for the future, via specifically-designed improvements in several high impact areas (shown in italics in the above diagram):

In this short review, the point has been made that biomass R&D must move beyond enhancing conversion technologies alone (analogous to petro-based chemical fractionations) and, for example, use biotechnology tools to re-design the feedstock for specific products. In addition, biotechnology opens the door for future success by being useful in an integrated product design strategy—for example, where feedstock and bioconversion can both be designed to allow optimal interaction in the system. Currently, such integrated approaches, requiring broad scientific coordination, managed teamwork, and complex intellectual property agreements, are not being given high enough priority for R&D support funding. Even in conventional starch to ethanol processes we see contradictory strategies: e.g., particular research to develop thermophilic enzymes, knowing that this requires more heat energy in the process, while practical research has focused on decreasing the temperature of the process to save energy. Biomass has potential as a feedstock and biotechnology has the potential to remove the decades-old hurdles⁷, but we need a unified strategy if a white knight is to appear. An integrated cross-discipline strategy will be vital to making large enough technical and economic breakthroughs for biomass utilization to contribute to any future sustainable energy platform.

2.McLaren JS (2005). Crop biotechnology provides an opportunity to develop a sustainable future. Trends in Biotech 23, 339-342

3.Finkelstein et al. (Editors) (2004) Proceedings of 25^th Symposium on Biotechnology for Fuels and Chemicals. Applied Biochemistry and Biotechnology 113-116, 1-1223, Humana Press, New Jersey

4.Monsanto (2005) http://www.monsanto.com/monsanto/us_ag/layout/
enhanced_value/pro_per/pro_per_corn/hfc.asp

5.Renewable Fuels Association (2002) http://www.ethanolrfa.org/RFA_Fuel_Cell_White_Paper.PDF

6.Sanford et al. (2004). Designing and building cell factories for biobased production. Genetic Engineering News 24, 1-4. (at http://www.genengnews.com)

7.McLaren JS (2000). Future renewable resource needs: will genomics help? J. Chem Technol Biotechnol 75, 927-932

James S. McLaren
StrathKirn Inc.
Chesterfield, MO
mclaren@strathkirn.com