Short-rotation Intensive Culture Research Articles

Input-output analysis of energy requirements for short rotation, intensive culture, woody biomass

A production model for short rotation, intensive culture (SRIC) plantations was developed to determine the energy and financial costs of woody biomass. The model was based on hybrid poplars planted on good quality agricultural sites at a density of 2100 cuttings ha −1, with average annual growth forecast at 16 metric tonne, oven dry (Mg(OD)). Energy and financial analyses showed preharvest costs of 4381 megajoules (MJ) Mg −1 (OD) and $16 (U.S.) Mg −1 (OD). Harvesting and transportation requirements increased the total costs to 6130 MJ Mg −1 (OD) and $39 Mg −1 (OD) for the delivered material. On an energy cost basis, the principal input was land, whereas on a financial basis, costs were more uniformly distributed among equipment, land, labor, and materials and fuel.

Poplar woody biomass yields: A look to the future

Yield increases of 2 to 3 times have been achieved for some agricultural crops over 40 years because of improved genetic material and culture. These increases suggest that similar yield increases might be achieved in short-rotation intensive culture (SRIC) energy plantations. Current poplar SRIC record small-plot yields are 4 to 7 times greater than average field yields. SRIC yields necessary for marginal profitability have not yet been attained in the field, but field yields are expected to increase based on the gains recently achieved in small experimental plots. The rate and potential size of future yield increases are uncertain, however. Whether the large yield gains achieved recently in agricultural crops can be duplicated in SRIC within a reasonable time will depend on a number of factors, including future investment in cultural and breeding research, and the realization of the biotechnology potential.

Short-Rotation Energy Plantations in North Central United States: An Economic Analysis

Abstract Interest in using intensive silviculture to produce high yields of biomass for energy has increased remarkably in the north central region of the United States. The North Central Forest Experiment Station is cooperating with others in establishing trial plantations throughout the north central region to obtain accurate estimates of biomass yields and costs of producing biomass for energy. The financial attractiveness of two woody biomass plantation alternatives for agricultural land was investigated—a basic short-rotation intensive culture plantation system on average agricultural land and a system on erodible agricultural land that is eligible for government financial incentives. Early growth from selected trial plantations has been greater than expected. However, with the recent energy glut in the United States, forecasted prices that potential users of woody biomass would be willing to pay have gradually decreased because of declining fossil fuel prices. In light of these two recent changes, the system on average agricultural land resulted in a negative financial performance while the system on erodible agricultural land with government financial incentives resulted in a positive financial performance.

Cost parameters affecting multiple rotation SRIC biomass systems

Short rotation intensive culture (SRIC) plantations were analyzed to determine a least-cost method of supplying feedstock for liquid fuel manufacturing. The plantations were based uponPopulus hybrid, nonfertilized and fertilized strategies and a spacing of 21,000 trees/ha. Financial analyses indicated a 3-y rotation would minimize production costs for the particular design of these plantations.

Financial selection of rotation age for SRIC plantations

Short rotation intensive culture (SRIC) plantations, established in central Pennsylvania, were analyzed to determine their economic optimum rotation age. The general management design for the plantations used fertilized and non-fertilized strategies, a tree spacing of 0·48 m 2 and a rotation length of 4 years. A stand-level financial model analyzed the unit cost of production for alternate rotation lengths based upon the plantation's investment and operating costs and resulting biomass yields. Analysis of the first two rotations indicated that the minimum unit cost for fertilized and non-fertilized strategies was in the fourth year of the first rotation and the third year of the second rotation. Growth curves for the rotations also showed a maximum volume production at the same points in the rotations. Selection of a 3-year rather than 4-year harvest during the second rotation would reduce unit costs by 14% in the non-fertilized strategy and by 15% in the fertilized strategy.

Mechanization of the operational aspects of short-rotation forestry

The International Energy Agency (IEA) has recognized the importance of the proper use of current technologies in researching the concept of biomass as a renewable energy source. An early program included one project that dealt entirely with the mechanization of harvesting trees grown under short-rotation intensive culture (SRIC) forestry. The Bioenergy Agreement that ended 31 December 1988 expanded this involvement with mechanization by creating a separate Activity called ‘Production Technology’. This Activity investigated the current state of technology for establishing, managing and harvesting SRIC forests or plantations. Five countries participated: Canada, Denmark, Sweden, the UK, and the US. Several workshops were held, and a final joint project evolved. As the final effort, a ‘Sourcebook’ of Production Technology will be made available. A summary of the main findings is provided here. This document will be published by the IEA and updated in future years as needed.

Coppicing success of young Eucalyptus saligna in Hawaii

Coppicing characteristics of felled 3-year-old E. saligna trees growing in Hawaii were evaluated for four DBH classes and two stump-height segments. About 40% of all the stumps had at least one living shoot > 2 cm at the end of the 20-week study period. Tree size before felling had no effect on number of dormant buds available to develop into shoots, sprouting success or length of the longest sprout per stump, but all of these variables were affected by stump-height segment. Standardized 20-cm stump segments above the lowest branch scars (about 34–60 cm above ground) had about double the number of dormant buds, sprouting success and length of the longest shoot per stump than stump segments below the lowest branch scars. Ambrosia-beetle attacks on the stumps were coincidental with coppice development (2–8 weeks after felling), and were less severe on the stumps from the smaller trees and on the upper stump segments. Reasons for the low coppicing success of E. saligna in Hawaii are unknown. The opportunity for coppice (frequency of dormant buds) and the disturbance of coppicing by ambrosia beetles need to be more fully understood before coppicing can be a dependable method of regenerating this species in short-rotation intensive culture plantations in Hawaii.

Developing financial and energy accounting models for woody biomass systems

A system of accounting models was developed for short rotation intensive culture (SRIC) Populus plantations to determine the financial and energy costs involved in supplying woody biomass feedstock to a conversion process. The models established the variable and fixed cost structure of alternate strategies proposed for growing, harvesting and storing the product. The least cost pattern of supply had financial costs of $65 per oven-dry metric tonne (Mg −1(OD)) and energy costs of 8901 megajoules (MJ) Mg −1(OD). Limitations to the models included adherence to a fixed technical design and production level for each of the alternate strategies and the use of point estimates for production and pricing coefficients.

Biological and economic potentials of Eucalyptus grandis and slash pine as biomass energy crops

Various cultural factors influence the biological and economic potentials of Eucalyptus grandis and slash pine as biomass energy crops for southern and northern Florida, respectively. On muck soil, superior E. grandis progenies may produce up to 70 dry Mg ha −1 in 24 months. However, coppicing success on muck soil has been inconsistent. Clones superior in frost-resilience and vigor and propagated as rooted cuttings have increased productivity potential on sandy soils. Break-even costs GJ −1 range from just under US$2 for E. grandis short-rotation intensive culture (SRIC) on muck soils (10 000 trees ha −1 with a 6-year rotation, i.e. seedling/coppice/coppice cycles of 2 years each) to US$4.00 GJ −1 on sandy soils. Planting density, but not coppice rotation, is sensitive to the discount factor. Through 8 years, slash pine yields responded well to soil amendments on typical sites and to high planting densities. Fertilization and vegetation control increased productivity some seven times over conventional culture through 5 years. For slash pine SRIC, higher discount rates increased initial stocking levels and shortened rotations. Break-even costs for slash pine are within the range of values estimated for E. grandis.

Biomass yield potential of short-rotation hardwoods in the great plains

Wood for fuel has increased in importance. Its primary use in the world is for energy, increasingly coming from wood wastes and new biomass sources. One solution to the potential problem of using high-quality trees for fuel could be woody biomass grown under a short-rotation intensive culture system. Species, size, age and spacing are factors that affect biomass production of broadleafed trees. Trials of several species grown at close spacing (0·3 m x 0·3 m) and cut at various ages are described and related to the growth and yield of more conventionally spaced plantings on an alluvial site in eastern Kansas.

Comparative growth analysis of five first year establishment poplar clones (Populus sp.) grown under a short-rotation intensive culture system

Comparative growth analysis of five first year establishment poplar clones (Populus sp.) grown under a short-rotation intensive culture system

Silver Maple Seed Sources for Increased Biomass Production

Abstract Silver maple shows promise for use in short-rotation intensive culture energy plantings. A seed source study composed of trees from 26 midwest locations was established in south-central Nebraska in 1979 to determine where silver maple seed should be collected for use in the central Great Plains. Trees were evaluated for survival, height growth, and number of dominant stems per tree during their seventh growing season. Sources from eastern Nebraska, western Iowa, eastern Kansas, and northwest Missouri generally exhibited the greatest survival, height growth, and number of dominant stems. Height growth appears to be under stronger genetic control than stem number, suggesting that selection for height should take priority when selecting trees for biomass production. Geographic trends related to survival and height growth, but not stem number, were observed. Environmental or geographic factors that are strong predictors of seed source performance could not be identified. Planting the most locally produced seed is advisable for the central Plains. North. J. Appl. For. 5:180-184, Sept. 1988.

Economic evaluations of multiple rotation sric biomass plantations

A series of short-rotation intensive culture (SRIC) Populus plantations involving four management strategies (control, fertilization, irrigation, and fertilization-irrigation) were evaluated in tandem with alternate harvesting and storage strategies to determine the least cost method for supplying biomass to an ethanol conversion facility. The plantations were based on Populus hydrid NE-388, a tree spacing of 0.6 m × 0.8 m, and a rotation length of four years. First rotation yields from the various strategies ranged from 33 to 42 oven-dry metric tonne per hectare (Mg(OD) ha −1). An average yield increase of 12% was realized from the second rotation coppice plantations. The control strategy had the lowest production costs for the two rotations, averaging 532 Mg −1 (OD). Harvesting and storage requirements nearly doubled the final costs, with the least cost system having an average total cost of $66 Mg −1 (OD). Over 50% of the total cost originated from equipment and material inputs, with labor costs representing nearly 30% of the total and land the final 20%.

Irrigating short rotation intensive culture hybrid poplars

Irrigating hybrid poplars in northern Wisconsin, a cool humid temperate area, resulted in consistent growth increases. Maintaining field soil moisture tensions higher than −0·07 MPa and probably higher than −0·03 MPa resulted in the greatest biomass yields. Height growth increases ranged from 2 to 22% for 1- to 4-year-old trees, and biomass increases ranged from 27 to 33% for 3- to 5-year-old trees. Irrigation produced an added 8·0 Mg ha −1 of accumulated biomass in a 5-year-old plantation. Consumptive water use during the growing season was from 4·4 to 4·8 mm day −1. Irrigation had little effect on growth and no effect on tree survival during the establishment year. After the first year, increased number of irrigations were required to maintain the designated soil moisture tension levels. This suggests that the primary benefits of irrigation in northern Wisconsin may occur from cumulative biomass increases during the rotation rather than from improved survival during establishment.

Economics of short-rotation intensive culture for the production of wood energy feedstocks

We review research and evaluate the economics of short-rotation intensive culture (SRIC) for the production of wood energy feedstocks in six regions of the U.S. The economics of SRIC are evaluated for present conditions under two sets of assumptions about anticipated advances in technology. The results show that delivered SRIC feedstock costs using available technology are likely to range between $3.00 and $4.10/GJ. Based on estimates of technological advances in tree breeding and selection, cultural management, and harvesting, delivered costs could be lowered to under $2.00/GJ. Advances in genetics, cultural management, and harvesting needed to reduce SRIC costs are technically attainable by the year 2000.

Wood Energy Plantation Economics in the Great Plains

Short-rotation intensive culture (SRIC) is a method of producing wood energy feedstocks that is potentially competitive with conventional wood sources in eastern Kansas. Silver maple is used as a representative energy species to examine alternative cutting cycles and planting densities. The sensitivity of discounted average cost is also evaluated with respect to changes in biomass productivity and to changes in production and harvesting costs. The results show that SRIC wood feedstocks can be grown, harvested, and delivered at costs approaching $50/dry tonne. This cost is nearly competitive with prices of delivered wood chips from conventional forest sources in eastern Kansas.

Energy from biomass and wastes: 1985 update and review

The gradual and then rapid reduction of crude oil prices, the impact of U.S. Gramm-Rudman-Hollings legislation (to reduce budget deficits) on R&D (research and development) budgets, the partial elimination of renewable-energy tax credits, and the possible elimination of all energy tax credits and forgiveness via tax reform, are all taking their toll on energy research and commercialization ventures. However, it appears that “biofuels” will survive and continue to exhibit modest increases in contributions to primary energy demand. A comprehensive assessment of renewable-technology options has shown that biofuels is the only option capable of making significant contributions to all energy sectors. The total contribution of renewable energy to primary energy demand in the U.S.A. is about 7.2EJ/y (6.8 quad/y); biofuels provide about 40% of the total. Research on short-rotation intensive-culture (SRIC) trees and herbaceous and aquatic biomass has identified specific species for development. Some of these species appear to be near economic feasibility as energy crops now. Commercialization of biomass and waste combustion systems has shown a spurt in growth because of the business opportunities offered by laws encouraging cogeneration. Thermochemical gasification research on advanced technology systems has reached the point where scale-up is being considered. Commercialization of state-ofthe-art technologies has slowed, but applications for small-scale producer gasifiers, particularly in developing countries, continue to expand. Thermochemical liquefaction research has concentrated mainly on high-temperature pyrolytic conversion methods that can increase yields and selectivities. Significant research achievements have been made in anaerobic digestion, but whatever its future as a large-scale source of methane, it is clear that digestion capacity will have to increase many-fold before biological methane can attain its potential. The mandated reduction in lead content of gasolines presents substantial marketing opportunities to alcohol-fuel producers. If projections for ethanol-fuel markets materialize, conversion of low-cost lignocellulosic materials will be necessary. Research to develop this technology is now in progress.

Short-rotation intensive culture for the production of energy feedstocks in the US: A review of experimental results and remaining obstacles to commercialization

Short-rotation intensive culture (SRIC) research has demonstrated that biomass yields can be substantially increased over those for conventional forestry. Moreover, this research has shown that the concept is technically feasible, and that costs of production are potentially competitive. The greatest potential for cost reduction lies in genetics, which appears to have the promise to increase productivity by as much as 40%. The development of innovative harvesting equipment can further reduce production costs by 30% compared with costs now experienced with conventional equipment. Although stand management research is now completed with regard to defining proper practices, there nonethe-less remains the potential for further cost reduction (e.g. refinement of yield-response relationships for various management practices). Many experimental plots are now entering the coppice stage. Productivity gains are almost certainly possible with development of management practices for established rootstocks. The ultimate test of the concept will require the demonstration of much larger monocultural plantations to identify uncertainties and financial risks.

Species Trials for Biomass Production on Abandoned Farmland

Abstract As part of a nationwide study of the potential for woody crops to supply biomass for energy use, we evaluated seven hardwood tree species and six hybrid poplar clones on four different sites in Vermont, with three fertilizer treatments on some sites. Not all species were evaluated on all sites. Plots containing 25 trees were replicated three or four times at each site. Trees were planted at a spacing of 0.6 x 0.6 m or 0.9 x 0.9 m and grown for 3 years. The application of fertilizer did have significant effect on height, diameter, and stem weight. Species with high yields (about 16 oven-dry t/ha/year) included four of the hybrid poplars. Silver maple, black locust, and the other two hybrid poplars yielded about 10 oven-dry t/ha/year. Based on growth alone, these species and clones were recommended for short-rotation intensive culture in areas with similar climate and growing sites. North J. Appl. For. 2:43-47, June 1985.

Crown architecture of short-rotation, intensively cultured Populus II. Branch morphology and distribution of leaves within the crown of Populus 'Tristis' as related to biomass production

The branch morphology and the distribution of leaves and specific leaf weight were determined within the crown of 5- and 6-year-old Populus 'Tristis No. 1' (P. tristis Fisch. × P. balsamifera L.) trees grown in northern Wisconsin under short-rotation, intensive culture at 1.2- and 0.6-m square spacings, respectively. The relationship of leaf area to aboveground biomass productivity was also evaluated for the same trees. The first-order branches within the trees exhibited acrotony and were predominantly long shoots. No branching higher than third-order was observed. Leaf size and specific leaf weight were greatest on the current terminal shoot and decreased from the upper portion of the crown to the base. When the 6-year-old trees were divided into eight 1-m vertical strata, over 80% of the total number of leaves and total leaf area was in three middle strata (4–7 m), and most of the 1-m strata contained leaf area attached to two or more height growth increments. Leaves attached to branches on a single height growth increment of the 6-year-old trees occurred in up to four 1-m vertical strata. Long shoots comprised 53% of total leaf area in the 5-year-old trees and 66% in the 6-year-old trees, short shoots the remainder. Ninety-five percent of the long shoots in the 6-year-old trees were in the three uppermost vertical strata (5–8 m), and 95% of the short shoots were in the lowermost leaf-containing vertical strata (3–6 m). Long-shoot leaves had higher specific leaf weights than short-shoot leaves attached to branches on the same height growth increment. Leaf-area indices (LAI) were 7.6 and 8.8 m2•m−2 for the 5- and 6-year-old stands, respectively. Leaf area per tree was linearly related to the aboveground biomass of the tree. The linear regression line for the relationship between leaf area and D2H (diameter2 × height) for the 6-year-old trees in the study was statistically different from that of the 5-year-old-trees. The data presented suggest that this relationship may serve as a useful quantitative index of crown closure in poplar stands. The results also suggest some crown morphological criteria useful for selection and breeding of improved poplar trees for short-rotation intensive culture.