Biofuel & Biomaterial Crops: We Might Be Doing It Wrong

As I was recently dulling blades while chopping switchgrass for some experiments, I started thinking whether the “high yield perennial grasses on marginal land” paradigm makes any sense for biofuels. There are many positives about using perennial grasses. They are low maintenance, high yield, require low additional nutrients, and have broad growing ranges.

However, even with these salient advantages and decent government funding, the “high yield perennial grasses on marginal land” paradigm has not yet become a reality. Three key elements seem to be holding it back.

1. Is the high lignin (woody biomass) content of these grasses, which accounts for the 15-20 percent of biomass that raises per acre yield above 10 tons, of real benefit or is it just a major interference to biomass conversion?
2. Is there an entrepreneurial agricultural community, including financial institutions, in the Eastern U.S. (which is targeted for these grasses) that could translate the perennial grass biomass paradigm into a profitable industry?
3. Is the very high value bio-carbon fiber market that is touted as the economic driver for these grasses a reality or merely a hopeful illusion? 

If these problems cannot be overcome quickly, is there another way to sustainably, and quickly, produce low-input non-food biofuel and biomaterial feedstocks that could create a sustainable Advanced Biofuel/Biomaterial industry? 

What follows are my thoughts on these questions. I can’t say they are completely worked out, but I hope there’s enough here to get the Advanced Biofuels/Biomaterial community to seriously consider this issue.

In his 2006 State of the Union Address, President George W. Bush spoke enthusiastically of a biofuels future that would be based on switchgrass. Stock prices of companies that sold switchgrass seeds soared and USDA/DOE bioenergy funding was quickly shifted to high yield perennial grasses. 

Unfortunately, eight years later there is no U.S. commercial implementation of a perennial grass system. (The recently dedicated POET prototype plant uses corn stover residue cellulose to produce ethanol.)

To explain this failure, the DOE/USDA approach was deficient in the following ways:

1. Instead of developing a processing model that was suited to the disbursed, small stands of perennial grasses, DOE clung to its biorefinery model that overlooked the transportation costs of biomass.
2. Crop improvement work focused on increasing yields and reducing nutrient inputs but little effort was put into understanding grass cell wall structure so that it could be more easily processed.
3. No programs were ever initiated to try ideas not in the preconceived DOE model.

And so, at the end of 2014, the acreage of switchgrass planted because of USDA bioenergy subsidies is rapidly disappearing as growers go back to more profitable crops. 

Could perennial grasses become sustainable biofuel crops?

Yes, but sufficient funding would have to be made available to correct the mistakes listed above. In addition the R&D would take the better part of a decade.

However, given the anti-biofuel focus of the Obama “Natural Gas is Good for the Environment” Administration and both parties in Congress, it is very unlikely this will happen any time soon.

Therefore, we must quickly begin the search for low-cost solutions we can implement immediately. Fortunately, I think there is a simple, sustainable, and successful alternative for the next decade that would create a multiproduct “advanced” biomass industry.

The Future is US Corn Ethanol Land

Contrary to the dire predictions of long-time corporate farming critics, anti-corn foodies, and several economists, the increase in U.S. corn planting needed to meet the 10 percent motor vehicle ethanol requirement did not result in a world-wide food price disaster. In fact, improvements stimulated by the ethanol market combined with stabilized ethanol demand, and financial speculators leaving agricultural futures for markets they could more easily manipulate, has led to corn prices around $3.70/bushel. This is close to prices in the 1970s and 1980s. (Since these prices are not corrected for inflation, corn is cheaper than it was thirty years ago.)

An Opportunity for an Advanced Biofuel & Biomaterial Renaissance 

With U.S. ethanol demand currently being capped by the Administration’s decisions on both RFS ethanol volume and E30 certification fuel, the combination of excess corn production and excess ethanol capacity will continue to drive both corn and ethanol prices lower.

With approximately 20-25 percent of current U.S. corn production being used for fuel ethanol, the questions for growers become:

• Could portions of this land be used for lower nutrient input biomass crops that would produce comparable income from ethanol or other biofuels and biomaterials?
• Could corn land not within current shipping distance of existing ethanol refineries also be used for biofuel/biomaterial crops?

I think the right answers to these questions could not only retain grower incomes but more importantly, could be an opportunity to build the foundation of a true Advanced Biofuel and Biomaterial system. This system would have the following characteristics.

• Biofuel/biomaterial crops would be low in lignin, but high in both C-6 and C-5 polysaccharides.
• These crops would be drought and excess moisture resistant and would not have human food use.
• The biomass would be easy to process into soluble sugars or polymers in the field with portable non-toxic, low-energy use units.
• These higher density and higher value soluble biofuel/biomaterial precursors could be transported hundreds of miles to multiproduct biorefineries.
• These biorefineries, larger than current corn starch ethanol plants, would also become crop independent since the input sugars or polymers would be the same no matter which plant species produced them.
• Some current ethanol plants could serve as the basis for these refineries.
• And, plant protein residues could continue to be used as animal feed.

Candidate Biofuel/Biomaterial Crops

So, what type of crops could serve as the basis for this system? A very good starting point would be root crops. Why? A root has the ground around it providing support. This support means a large quantity of biomass can be accumulated without the complex cell wall structure needed to support a plant stalk. Without that structure, the primary cell walls of the root can be more easily accessed by enzymes. This means a quicker, less expensive biomass conversion process is possible.

A Place to Start

Seed companies have been developing non-food sugar beets that they call Energy Beets. If energy beets were substituted for corn, preliminary estimates based on current energy beet yields and sugar conversion yields (Atlantic Biomass data) show that energy beets could provide similar income for growers

Comparison of Energy Beets and Corn

If the yields could be maintained, the acreage needed to produce current ethanol levels from energy beets could be significantly reduced. This could produce opportunities for additional beet acreage to be used for bio-jetfuels or biomaterials. In addition, other root crops, especially ones that could provide medium to high-value polymers should be considered for specialty markets.

The result of the switch from ethanol corn to general use biofuel/biomaterial crops could provide the reliable supply of biomass feedstock needed to create and sustain a diverse Advanced Biofuel and Biomaterial industry.

By so doing, it would create a financial climate that would bring private investors back to the arena. Researchers on the crop development side would have the money to develop lower input, higher yield crops while biochemists and biologists could bring new bio-based polymers to market as well. And, who knows, maybe even easier to process perennial grasses that could be grown on marginal lands could be developed as well!

Lead image: Switchgrass via Shutterstock