Timothy A. Volk

Life cycle assessment of a willow bioenergy cropping system.

Abstract The environmental performance of willow biomass crop production systems in New York (NY) is analyzed using life cycle assessment (LCA) methodology. The base-case, which represents current practices in NY, produces 55 units of biomass energy per unit of fossil energy consumed over the biomass crops 23-year lifetime. Inorganic nitrogen fertilizer inputs have a strong influence on overall system performance, accounting for 37% of the non-renewable fossil energy input into the system. Net energy ratio varies from 58 to below 40 as a function of fertilizer application rate, but application rate also has implications on the system nutrient balance. Substituting inorganic N fertilizer with sewage sludge biosolids increases the net energy ratio of the willow biomass crop production system by more than 40%. While CO2 emitted in combusting dedicated biomass is balanced by CO2 adsorbed in the growing biomass, production processes contribute to the systems net global warming potential. Taking into account direct and indirect fuel use, N2O emissions from applied fertilizer and leaf litter, and carbon sequestration in below ground biomass and soil carbon, the net greenhouse gas emissions total 0.68 g CO 2 eq . MJ biomass produced −1 . Site specific parameters such as soil carbon sequestration could easily offset these emissions resulting in a net reduction of greenhouse gases. Assuming reasonable biomass transportation distance and energy conversion efficiencies, this study implies that generating electricity from willow biomass crops could produce 11 units of electricity per unit of fossil energy consumed. Results form the LCA support the assertion that willow biomass crops are sustainable from an energy balance perspective and contribute additional environmental benefits.

Renewable Energy from Willow Biomass Crops: Life Cycle Energy, Environmental and Economic Performance

Short-rotation woody crops (SRWC) along with other woody biomass feedstocks will play a significant role in a more secure and sustainable energy future for the United States and around the world. In temperate regions, shrub willows are being developed as a SRWC because of their potential for high biomass production in short time periods, ease of vegetative propagation, broad genetic base, and ability to resprout after multiple harvests. Understanding and working with willows biology is important for the agricultural and economic success of the system. The energy, environmental, and economic performance of willow biomass production and conversion to electricity is evaluated using life cycle modeling methods. The net energy ratio (electricity generated/life cycle fossil fuel consumed) for willow ranges from 10 to 13 for direct firing and gasification processes. Reductions of 70 to 98 percent (compared to U.S. grid generated electricity) in greenhouse gas emissions as well as NOx, SO2, and particulate emissions are achieved. Despite willows multiple environmental and rural development benefits, its high cost of production has limited deployment. Costs will be lowered by significant improvements in yields and production efficiency and by valuing the systems environmental and rural development benefits. Policies like the Conservation Reserve Program (CRP), federal biomass tax credits and renewable portfolio standards will make willow cost competitive in the near term. The avoided air pollution from the substitution of willow for conventional fossil fuel generated electricity has an estimated damage cost of

Biomass and nutrient removal by willow clones in experimental bioenergy plantations in New York State

0.02 to

Growing fuel: a sustainability assessment of willow biomass crops

0.06 kWh−1. The land intensity of about 4.9 × 10−5 ha-yr/kWh is greater than other renewable energy sources. This may be considered the most significant limitation of willow, but unlike other biomass crops such as corn it can be cultivated on the millions of hectares of marginal agricultural lands, improving site conditions, soil quality and landscape diversity. A clear advantage of willow biomass compared to other renewables is that it is a stock resource whereas wind and PV are intermittent. With only 6 percent of the current U.S. energy consumption met by renewable sources the accelerated development of willow biomass and other renewable energy sources is critical to address concerns of energy security and environmental impacts associated with fossil fuels.

Energy feedstock characteristics of willow and hybrid poplar clones at harvest age

The development of short-rotation intensive cultural (SRIC) willow systems as a source of bioenergy and bioproducts is growing in the northeastern and midwestern United States. Important data for sustainable management such as nutrient removal and nutrient use e8ciency in willow bioenergy plantations is lacking. This study reports wood biomass production, annual removal of nutrients, and nutrient use e8ciency in experimental plantings of SRIC willow and poplar at Tully, New York. E9ects of clone, fertilization, irrigation, planting density, and harvest cycle were analyzed. Annual biomass production of 15 –22 dry Mg=ha removed 75 –86, 10 –11, 27–32, 52–79 and 4 –5 kg=ha=year of N, P, K, Ca and Mg, respectively. For all the variables studied, the responses depended on clone. Fertilization and irrigation increased rates of nutrient removal by means of increased biomass production. Unlike planting density, harvest cycle signiBcantly a9ected rates of nutrient removal and nutrient use e8ciency. For clone SV1 ( Salix dasyclados), an irrigated and fertilized planting with a density of 36,960 trees=ha harvested on a 3-year rotation had the highest biomass production and nutrient use e8ciency, and the lowest rates of nutrient removal. The annual harvest cycle had the lowest nutrient use e8ciency and the highest annual removal of nutrients suggesting that this choice would be most appropriate for biomass crops that are to be used as bu9er strips to manage nutrient runo9 from agricultural Belds. An appropriate choice of clone, planting density, and harvest cycle could tailor the rates of nutrient removal and nutrient use e8ciency to match the objective of the planting. c 2001 Elsevier Science Ltd. All rights reserved.

Willow biomass production during ten successive annual harvests

2to the atmosphere. The implementation of good management practices will maintain productivity over multiple rotations. Rural development and environmental benefits associated with deployment and use will accrue to the local community because of the willow system’s short supply chain. The economic valuation of these benefits are necessary for the deployment of woody crops, which in turn can help society become more sustainable.

Effect of organic amendments and slow-release nitrogen fertilizer on willow biomass production and soil chemical characteristics

Abstract Woody biomass feedstock produced from willow and hybrid poplar can be converted into bioenergy via thermochemical and biochemical processes. Variation in key properties that relate to the quality of biomass feedstock and determine its value for energy conversion were determined at rotation age (3 years), in 30 willow and seven hybrid poplar clones, grown in a short-rotation intensive culture (SRIC) system in central NY. Substantial clonal variation in the concentrations of nitrogen (2.9– 5.0 g kg −1 ), phosphorus (0.4– 0.8 g kg −1 ) potassium (1.2– 2.4 g kg −1 ), sodium (0.09– 0.20 g kg −1 ), calcium (3.9– 8.9 g kg −1 ), magnesium (0.2– 0.6 g kg −1 ), ash (13.2– 27.2 g kg −1 ) and bark percentage (3.6–8.1%) was found in stem (bark+wood) samples. A lower amount of variation was documented for specific gravity (0.33– 0.48 g cm −3 ) and percent moisture (49–56%). Bark had a higher concentration of inorganic elements and ash, relative to wood. Willow clones as a group had a higher specific gravity, bark percentage and calcium concentration relative to hybrid poplar clones, which had a higher potassium concentration. The two groups were similar in terms of the concentrations of other elements and ash. Clonal variation in these characteristics present opportunities for manipulating feedstock quality through selection, breeding and plantation management.

Sustainability and environmental issues associated with willow bioenergy development in New York (U.S.A.).

Abstract Five willow clones and one hybrid poplar clone were planted during 1987 at 0.3×0.3 m spacing and harvested annually for 10 years. Half of the trees were fertilized annually with N, P and K and all trees were irrigated beginning in the third growing season. Annual biomass production fit the logistic growth curve well for four of the clones with r 2 values ranging from 0.91 to 0.54, suggesting that well-adapted willow clones can be consistently productive for at least 10 years with annual harvesting. Fertilizer did not increase the maximum biomass production level attained, but it reduced the time required to reach maximum production by 1 year. The correlation between annual biomass production and the number of growing degree days during years 4–10 was high, ranging from 0.95 to 0.66.

Fifty years of change in an upland forest in south-central New York: general patterns

Abstract Lime-stabilized sewage sludge and composted poultry manure, at a rate of 250 m 3 ha −1 each, and slow-release N fertilizer (Scotts Osmocote) at 100, 200 and 300 kg N ha −1 , were applied to plots of willow biomass crops during the first season of a three-year growth cycle. Stem biomass production was measured annually and soil chemical characteristics were assessed at the end of the growth cycle. Average annual stem biomass production was 8– 11 Mg ha −1 in slow-release N fertilized plots corresponding to a yield increase of 7–33% relative to control plots. In organically amended plots, annual stem biomass production increased by 30–38% relative to control plots. The study suggests that organically amended willows grew at a slightly faster rate than slow-release N fertilized willows. Statistically, the relationship between slow-release N application rate and stem biomass production was not highly significant; applications of slow-release N in excess of 100 kg N ha −1 provided no additional yield benefits. Differences in soil characteristics were most strongly expressed in surface soil. The pH at 0– 10 cm depth was 1 and 2 units higher on lime-stabilized sludge and composted poultry manure plots, respectively. Concentrations of soil K, P and Mg were dramatically higher in the composted poultry manure soils. The highest soil organic matter and N levels were observed in the surface horizons of organically amended soils. Utilization of organic residuals increases biomass production, provides beneficial use for wastes, reducing production costs and contributing to the sustainability of biomass production systems.

Life-Cycle Assessment for the Production of Bioethanol from Willow Biomass Crops via Biochemical Conversion*

Abstract Biomass-for-bioenergy cropping and production systems based on willow (and poplar) planted and managed at high densities and short (3–4 year) coppice harvest cycles, providing fuel for co-firing with coal (or other types of energy conversion) must be ecologically and environmentally sustainable to be commercially successful. Current knowledge and ongoing research and development indicate that the production and utilization systems involved are environmentally and ecologically sustainable. Therefore two primary constraints to commercialization are being met. The remaining constraint is economic viability based on cost of production and use, the value of environmental externalities (such as atmospheric emissions), and potential government/public policy actions to promote this system of providing a locally produced and renewable farm crop and fuel. The environmental and ecological benefits of the system should act as a catalyst for developments needed to overcome the economic constraints of the system.