Sustainability is a requirement for all new biobased technologies. Sustainability is dependent upon; acceptable environmental impacts of products; economic viability for all participants; and a positive social impact of the product and its production. Over the past four years the Integrated Farming Systems group at Prosser, WA has been recommending that growers incorporate oilseed cover crops that contain glucosinolates in rotation to control soil pathogens and protect soil resources. Growers incorporating these cover crops have experienced savings of up to $130/ha by offsetting soil fumigation costs. As a result, the area planted to oilseed cover crops has increased from 400 to 8,000 ha (20,000 ac). In response to this increase we are developing an additional strategy that further improves farm profitability while maintaining the desired benefits of biofumigation. Currently, mustard cover crops and other oilseed green manures are planted and incorporated in the fall prior to reaching seed maturity. We have initiated a series of studies evaluating a number of oilseed crops grown to maturity for an emerging biodiesel market and how they will fit into current high value irrigated vegetable cropping systems. We are evaluating five oil seed crops that can be grown in the PNW, as well as, nationally. These include: spring and winter rapeseed, mustard, sunflower, safflower and soybean. For each of these crops the general production practices; date of planting, flowering, harvest date, oil production etc. fertility, pest management, irrigation and soil quality issues will need to be addressed for this industry to become sustainable and economically sound for U.S. agriculture. Our preliminary data indicates that approximately 7-15 million liters (2-5 M gallons) of biodiesel can be produced on the area currently growing the cover crop, using such crops as safflower or winter rapeseed. In the Midwest, production of biodiesel using soybeans averages 3.8 M liters (1 M gallons) on equivalent acreage.
Another bioenegy crop we are studying is switchgrass production and its conversion to ethanol. About 90% of the domestic ethanol feedstock supply is derived from corn grain (Zea mays L.). Reasons for having selected corn include: 1) corns’ high starch content which can be rapidly distilled to alcohol, 2) corns’ higher distillation efficiencies are greater than most other feedstocks, 3) most of the ethanol produced is in the mid-West where corn is widely grown, and 4) many refineries are located in the Gulf Coastal States, close to current ethanol distillation centers. Total dependence of the ethanol market on corn has inherent problems in sustaining feedstock supplies including: 1) as a warm-season crop, corn cannot be grown in all areas, such as those with short growing seasons or low rainfall, 2) corn requires high inputs of fertilizers, herbicides and insecticides to ensure high yields, 3) as an annual crop, corn grown under rain-fed conditions has yield potentials varying significantly from “bin busters to empty bins”, making it risky to grow due to the uncertainty of shifts in rain fall as a result of global climate change, and 4) wind erosion of soils resulting from annual cropping is a major problem in the arid west.
1. To determine adaptability of switchgrass based upon yield monitoring, fiber quality, cultivar selection, nutrient use efficiencies, weed control and irrigation requirements.
Preliminary research plot yields of 13.5 and 13.8 Mg/ha dry matter for switchgrass and grain corn, respectively, hectares needed to sustain a 38 million L per year ethanol facility would be 8,431 and 7,075 ha, respectively. When placed in context of the energy return balance of 4.4 and 1.2 (energy output:input ratio) for switchgrass and corn, respectively, corn will be a more expensive feedstock than switchgrass. Comparatively, irrigated corn producers currently grow high yields of grain while our preliminary switchgrass research indicates a significant potential for crop improvement and improved ethanol yields. To produce sustainable feedstocks as alternative energy supplies in the PNW we would likely see a shift from less profitable crops to those that meet feedstock demands while increasing grower returns.
Variety Trials: There are five major oil seed crops that can be grown in the PNW. These include: rapeseed, mustard, sunflower, safflower and soybean. For each of these crops the general production practices; date of planting, flowering, harvest date, oil production etc.
Fertility: Nutrients nitrogen, phosphorus and sulfur are most relevant. Importance will be related to soil types and irrigation rates. Yields can double under irrigation and affect fertilization optimums. Determine rates and timing of fertilizer application. Current recommendations are 1/3 pre-plant, 1/3 before flower, 1/3 after flower.
Irrigation: Determine threshold irrigation rates and timing for major soil types. Identify economics of irrigation.
Rotation Trials: How each of the oilseed crops (rapeseed, mustard, sunflower, safflower and soybean) fits into an irrigated vegetable/potato based rotation. Incorporation of biofuel crop before or after potatoes, etc to maximize economic return. Also, implications to disease severity of the crops within the rotation.
Insect and Disease Impacts: Determine the impact of each oilseed crop on soilborne pathogens and insects. Example: sunflowers are known to harbor white mold, mustard can harbor leafhoppers. What is the impact if any on potatoes or other crops in rotation? Value added: use of oilseed residues as biological control agents of many soilborne diseases, for use in organic systems.
Soil Quality: Determine impact on soil quality. How, under irrigation inclusion of oilseed crops affect C, N, P and S cycling, soil organic matter, soil water relations, soil tilth properties (bulk density, infiltration, soil crusting etc.)
Life Cycle Energy Balance: To quantify the total primary energy requirements and the overall energy efficiencies of processes and products. Understanding the overall energy requirements of biodiesel and ethanol production is vital in understanding the extent to which biodiesel made from oilseeds or ethanol made from switchgrasses are a renewable energy source. The more fossil energy required to make a fuel, the less the fuel is renewable. Energy efficiency estimates will determine how much additional energy must be expended to convert the energy available in raw materials used in the fuel’s life cycle to a useful fuel.
Socioeconomic Studies: Bioenergy production has the potential for assisting rural and farm development, aiding our national security through increased reliance on domestic renewable energy. Determine production sustainability, economic profitability and influence on local communities.