Ten fundamentals about bioenergy: Part 7 annual and perennial life cycles
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Fundamental #7: A variety of bioenergy crop species comprising both annual and perennial life cycles is critical to a successful bioeconomy.
This is the seventh in a series of articles on bioenergy. The previous installment focused on perennial crops and this article will discuss the use of annual crops such as corn, forage sorghum, winter cereal rye, etc. as bioenergy feedstock sources. An emerging question in bioenergy circles is whether we should be growing annual crops or perennial crops for biofuel feedstock. To answer this question, one must keep in mind an important tenet of bioenergy: All biomass is local. Regional differences in climatic conditions, soil fertility, water availability, market access and processing capacity require a diverse matrix of available bioenergy crops. There is no “one size fits all” bioenergy crop. This inherent requirement for diversity includes life cycle (annuals, winter annuals, and perennials) in addition to a multiplicity of crop species.
The previous article explored the environmental advantages of perennial energy crop systems. Today we focus on annual crops, which offer advantages in grower marketing flexibility, biomass yield and if managed correctly, annual crops are also protective of the environment. The following are several advantages associated with annual crops.
Due to changing markets and input costs, growers may be hesitant to commit land to long-term rotations with perennials. Annual bioenergy crops provide a viable alternative to risk-averse producers.
Annual crops do not require the two to three-year establishment time to reach peak yield associated with perennial grasses like switchgrass and miscanthus. Annual crops will provide biomass feedstock tonnage quickly.
Biomass yield on a land area basis is often greater with annual crops, especially when used in conjunction with winter annual cover crops which can also be harvested for biomass.
Integrating annual crops with winter annual cover crops widens the window of biomass availability for biorefineries and spreads out income and weather related risk for growers.
Annual crops can be integrated with cover crops to improve environmental profiles by scavenging residual nitrogen and providing year-round ground cover.
All biomass is local and no single crop is a best fit for all localized growing conditions. Having a number of energy crop alternatives available to growers is critical to the success of the bioeconomy.
Read part 1, part 2, part 3, part 4, part 5, part 6, part 8, part 9, part 10 of this series.
