Short-term barriers to energy cropping

Posted Thursday, 8 November 2018, 15:23

Chelsea Petrenko and Stephanie Searle

All stages of advanced biofuel production face challenges, and an essential step to reliably scaling them across the transportation sector and beyond is ensuring the availability of feedstocks. Wastes and residues are finite, and sustainably-produced cellulosic energy crops represent one of the few low carbon feedstocks of which the supply can increase. These crops include Miscanthus, switchgrass, and short-rotation poplar and willow grown on low-carbon, unused land. Displacing a significant proportion of petroleum with advanced low carbon fuels in the future will require energy crops. However, extremely little feedstock is produced anywhere in the world today, despite substantial demand for biofuel in the U.S. and other countries. Three of the most salient barriers in energy cropping in the near-term involve issues with supply chain logistics, profitability, and natural resource constraints.

Supply chains for perishable commodities, such as corn grain, produce, and milk, have evolved over time to preserve products and deliver goods efficiently and at reasonable costs. Corn grain, for example, has a consistent shape and size, high energy density, and importantly, decades of supply chain research and development. However, these agricultural and transport practices for other commodities don’t necessarily work for energy crops, which are bulky, low density, and unstable if not dried before shipment. Transporting low-density energy crop biomass is inefficient because, although the trucks may be full, they deliver low mass of the needed crop.

Other challenges to the feedstock supply chain include contamination with soil after field drying and the need for modifying farm equipment to accommodate new crop types. Further, farms are often spread over long distances with little continuity in where the crops are grown, which makes transportation routes inefficient and expensive. Storage is also a challenge because large amounts of dried cellulosic biomass are susceptible to fire. Fire was caused by a lightning strike at one cellulosic biofuel facility.

As with any nascent industry, the costs of launching a new endeavor can outweigh the uncertain prospects of future profit. In the case of feedstock cultivation, high costs of entry can deter growers from making the switch.  Figure 1 shows the theoretical cumulative profit over decades of Miscanthus cultivation in Germany. A high initial investment is required for establishing a Miscanthus plantation, and this cost is not recuperated until approximately seven years after planting. It is understandable that growers would be wary of taking the leap without knowing the long-term viability of the market. Other studies, which relied on methods such as survey data collection from hundreds of stakeholders or modeling exercises, support these findings and have also shown that overall production costs, and specifically feedstock costs, are barriers to expanding the cellulosic biofuel industry. At present, cellulosic biofuels made from energy crops need government incentives to be economically viable, and political uncertainty regarding policy these incentives is another barrier to the advanced biofuel industry.

Cumulative profit of growing Miscanthus over time in Germany
Figure 1. Cumulative profit of growing Miscanthus over time in Germany. 

Water availability presents another fundamental challenge to scaling the deployment of advanced biofuels. While biofuel feedstocks are more drought tolerant than food crops, yields of most energy crop species are still sensitive to water availability, especially in arid regions, which further strains the profitability of growing. Our first-hand experience visiting cellulosic biofuel trials in Italy and Macedonia illustrated two different water availability scenarios: in Sardinia, though generally a dry environment, producers took advantage of under-utilized reservoirs to provide ample water throughout the growing season. Conversely, Macedonia enforced water rations among farmers, and tensions between existing food and tobacco farms and the small feedstock trials were already brewing. While much research has addressed the myriad implications of indirect land use change, an important, and potentially overlooked, aspect to consider is water allocation to food versus fuel.  Further, water limitations exacerbate the cost and logistical challenges to energy cropping. Innovation and investment may be able to overcome the other barriers discussed here, but water availability will pose a long-term challenge to the expansion of cellulosic biofuels.

Overcoming these barriers will be key to accelerating cellulosic biofuel feedstock cultivation and providing an adequate foundation for the growth of the industry. In another blog, we discussed the importance of government support for establishing cellulosic biofuel facilities in the U.S. Strong financial support for cellulosic biofuels is an important element to overcoming the economic challenges of this industry, but other, more direct measures to support energy cropping are important as well. In the U.S., some progress is being made. The DOE Bioenergy Technologies Office has been addressing logistical challenges by sponsoring research to modifying baling equipment to produce denser bales as well as tree harvest machinery to cut small-diameter trees. Farm extensions have been working to educate potential feedstock growers about these barriers. The Idaho National Laboratory’s library also provides extensive resources on crop viability in different environments, affordability of biomass crops by region, and strategies for successful cultivation and harvest, all of which may directly serve growers and help slowly start to overcome these barriers. With an increase in these efforts, as well as stronger and more stable policy incentives for cellulosic biofuels, it’s possible the hurdles to energy cropping can be surmounted.