Energy grasses can be used as feedstocks for bioenergy and biochemicals, as well as biofuels. So, while the future of the Renewable Fuels Standard, and consequently the demand for energy grasses for advanced biofuel production remain uncertain, developers are undeterred. Lux Research has reported that more than 1 billion metric tons of biomass per year would be needed to replace just 3% of total petroleum products.
Meeting this demand would require “feedstock innovations, such as crop modification, new value chain configurations, and agronomic technology improvements …,” the report adds. Understanding this need, several companies are involved in advancing biomass innovations.
Ceres Inc., Thousand Oaks, Calif., for example, has been focusing on energy-crop trait development. With a Department of Energy Advanced Research Projects Agency-Energy grant, Ceres conducted a multi-year study in several states to explore its biotech traits that would allow growers to produce higher-yielding energy crops with fewer crop inputs. In addition, Ceres confirmed the performance of its nitrogen utilization trait in switchgrass, miscanthus and sorghum.
Richard Hamilton, Ceres president and CEO, recently reported that the nitrogen utilization trait has translated into higher biomass yields — as much as 50% or more in some cases.
Ceres also has shown that its traits to increase juice volume and sugar content in sweet sorghum have advanced in its product development pipeline. Ceres has introduced sweet and high-biomass sorghum hybrids at ethanol mills in Brazil, and has formed a market development agreement with Syngenta AG, which is evaluating crop protection products to be used with the sorghum.
In the U.S., Ceres currently markets two high-biomass sorghum hybrids and three switchgrass varieties under the Blade Energy Crop brand. The company also is working on seeded miscanthus varieties in its research and development program.
Genera Energy Inc., Vonore, TN, is working on advancing energy-crop cultivars, as well as harvesting processes and equipment and supply-chain management.
“We’re focused on the development of turnkey biomass solutions,” says Sam Jackson, the company’s vice president of business development. Green Power Conferences presented a 2013 Sustainable Biofuels Award to Genera Energy in recognition of Genera’s work to enhance sustainability in feedstock production, collection and processing.
In terms of genetics, Genera Energy has been working with a number of private companies and public institutions to improve switchgrass, miscanthus, biomass sorghum and sweet sorghum cultivars.
Switchgrass can fit well into a grower’s production system because it is seeded and relatively easy to plant. It can also perform well on marginal soils. Growers can use conventional mowers, balers or choppers on switchgrass, Jackson says. In the Southeast, lowland varieties yield between 7 and 8 dry tons/acre, while upland varieties in more northerly areas produce 4 to 5 dry tons/acre, he adds. With proper maintenance, a switchgrass stand can last for 20 to 25 years.
Miscanthus is more expensive to establish than switchgrass because it is vegetatively propagated. However, once it matures in three years, miscanthus can yield 10 to 12 dry tons/acre. With proper maintenance, a miscanthus stand will last for seven to 10 years.
Meanwhile, biomass sorghum and sweet sorghum are seeded annuals and would fit into more of a conventional row-crop rotation, Jackson says. Biomass sorghum can be grown anywhere that corn is grown, he adds. Biomass sorghum, which can reach a height of 15 ft., produces about 10 dry tons/acre. Together with perennial crops, such as switchgrass and miscanthus, annual sorghum crops provide flexibility in the feedstock supply chain.
Sweet sorghum yields are measured by gallons or liters of biofuel produced per acre or hectare. Anna Rath, CEO of NexSteppe, South San Francisco, CA, says in Brazil, NexSteppe’s Malibu sweet sorghum hybrids have been used as a complement to sugarcane to provide additional feedstock for existing sugar-to-ethanol mills. A typical sugarcane crop grows for five years, after which time growers either let the land lie fallow or plant it to a cover crop. Sweet sorghum can be grown at this time.
“Malibu hybrids are capable of yielding well above the 2,000 liters/hectare needed to make them a compelling crop for Brazilian mills,” Rath says.
In addition to six Malibu sweet sorghum hybrids, NexSteppe has released a high-biomass sorghum hybrid called Palo Alto. The company has sold more than 1,000 hectares of its sorghums in Brazil this season.
“More broadly, we’ve trialed them in 10 states and with commercial partners in 12 countries on five continents,” Rath says.
In dryland conditions, Palo Alto yields about 8 dry tons/acre, and about 14 dry tons/acre under more optimal conditions, Rath says. Palo Alto’s low moisture levels at harvest help reduce harvesting and transportation costs, and make it a drop-in feedstock for biomass boilers, she adds.
Speaking of harvesting, Genera Energy has been working on improving harvest economics. Growers who were producing high-volume energy grasses for Genera Energy were getting about 15 to 20 bales/acre, which then had to be picked up in the field.
“They were spending more time handling the bales after harvesting than they did creating them,” Jackson says. As a result, Genera Energy began testing self-propelled field harvesters manufactured by New Holland, John Deere and Claas, to name a few. These harvesters could be used to blow materials into semitrucks parked in the fields, thus handling the biomass more quickly.
The next challenge is bulk density — it is more economical to transport large square bales with a bulk density of 12 to 14 lbs./cu. ft. versus chopped biomass with a bulk density of just 5 to 6 lbs./cu. ft., Jackson says. Therefore, Genera Energy has been evaluating ways to compact the biomass in the truck, similar to what the municipal solid-waste industry does. The compactor’s additional weight on the truck, however, could also create problems, especially on rural roads.
More research on overcoming these challenges, including using a stationary hydraulic ram technology, is being conducted.
Jackson says while the demand for energy grasses for biofuels is not huge right now, Genera Energy sees tremendous growth ahead in the biochemical and thermochemical businesses. Its business model, he adds, is to offer turnkey solutions to clients — be they cellulosic ethanol plants, biochemical producers or utility companies — anywhere in the country, and contract with growers near those given facilities.
Similarly, NexSteppe’s business model is to sell energy-crop seed to the facilities which, in turn, would likely contract with growers. While the infrastructure for the cellulosic ethanol industry in the U.S. is developing more slowly than in Brazil, Rath is optimistic about the medium- and long-range opportunities here.
These energy-crop developers agree that the RFS has been an excellent tool to drive the development of biofuels and hope it remains in place. Even if biofuel requirements in the RFS are reduced, though, the developers see promising markets down the road — markets that could conceivably require a billion metric tons of biomass per year.