Harvesting productivity and costs when utilizing energywood from pine plantations of the southern Coastal Plain USA

For woody biomass to make a significant contribution to the United States' energy portfolio, harvesting contractors must economically harvest and transport energywood to conversion/processing facilities. We conducted a designed operational study in the Coastal Plain of North Carolina, USA with three replications of three treatments to measure harvesting productivity and costs when utilizing woody biomass. The treatments were: a conventional roundwood only harvest (control), an integrated harvest in which merchantable roundwood was delivered to mills and residuals were chipped for energy, and a chip harvest in which all stems were chipped for energy use. The harvesting contractor in this study typically delivers 2200–2700 t of green roundwood per week and is capable of wet-site harvesting. Results indicate that onboard truck green roundwood costs increased from 9.35 $ t⁻¹ in the conventional treatment to 10.98 $ t⁻¹ in the integrated treatment as a result of reduced felling and skidding productivity. Green energy chips were produced for 19.19 $ t⁻¹ onboard truck in the integrated treatment and 17.93 $ t⁻¹ in the chip treatment. Low skidding productivity contributed to high chip costs in the integrated treatment. Residual green biomass was reduced from 18 t ha⁻¹ in the conventional treatment to 4 and 3 t ha⁻¹ in the integrated and chip treatments, respectively. This study suggests that until energywood prices appreciate substantially, loggers are unlikely to sacrifice roundwood production to increase energywood production. This research provides unique information from a designed experiment documenting how producing energywood affects each function of a harvesting system.     

Industrial supply chains and production machinery of forest chips in Finland

Metsäteho Oy surveyed the industrial supply chains used in the production of forest chips in 2006 in Finland. The Metsäteho study also conducted a survey of the production machinery of forest chips used by energy plants in 2007, and provided an estimate of industrial supply chains and future machinery requirements for forest chip production in Finland.The majority of the logging residue chips and chips from small-sized thinning wood were produced using the roadside chipping supply chain in 2006. The chipping at plant supply chain was also significant in the production of logging residue chips. The majority of all stump wood chips consumed were comminuted at the plant, and with only around one fifth comminuted at terminals. The role of the terminal chipping supply chain was also significant in the production of chips from logging residues and small-sized wood chips. It was predicted that the roles of both terminal chipping of logging residues and chipping at the plant will increase by the year 2010. Regarding the production of chips from small-diameter wood, it was estimated that the role of chipping at the plant will also increase in coming years. The proportion of roadside chipping in the production of small-sized wood chips and logging residue chips is expected to decrease.The study estimated that a total of 1100 machine and truck units were employed in the production of forest chips for energy plants in 2007. Increasing forest chip consumption will create considerable demand for additional forest chip production resources in the future.     

Supply chain cost analysis of long-distance transportation of energy wood in Finland

The increasing use of bioenergy has resulted in a growing demand for long-distance transportation of energy wood. For both biofuels and traditional forest products, the importance of energy efficiency and rail use is growing. A GIS-based model for energy wood supply chains was created and used to simulate the costs for several supply chains in a study area in eastern Finland. Cost curves of ten supply chains for logging residues and full trees based on roadside, terminal and end-facility chipping were analyzed. The average procurement costs from forest to roadside storage were included. Railway transportation was compared to the most commonly used truck transportation options in long-distance transport. The potential for the development of supply chains was analyzed using a sensitivity analysis of 11 modified supply chain scenarios.For distances shorter than 60 km, truck transportation of loose residues and end-facility comminution was the most cost-competitive chain. Over longer distances, roadside chipping with chip truck transportation was the most cost-efficient option. When the transportation distance went from 135 to 165 km, depending on the fuel source, train-based transportation offered the lowest costs. The most cost-competitive alternative for long-distance transport included a combination of roadside chipping, truck transportation to the terminal and train transportation to the plant. Due to the low payload, the energy wood bundle chain with train transportation was not cost-competitive. Reduction of maximum truck weight increased the relative competitiveness of loose residue chains and train-based transportation, while reduction of fuel moisture increased competitiveness, especially of chip trucks.     

Techno-economic assessment of pellets produced from steam pretreated biomass feedstock

Minimum production cost and optimum plant size are determined for pellet plants for three types of biomass feedstock – forest residue, agricultural residue, and energy crops. The life cycle cost from harvesting to the delivery of the pellets to the co-firing facility is evaluated. The cost varies from 95 to 105 $ t⁻¹ for regular pellets and 146–156 $ t⁻¹ for steam pretreated pellets. The difference in the cost of producing regular and steam pretreated pellets per unit energy is in the range of 2–3 $ GJ⁻¹. The economic optimum plant size (i.e., the size at which pellet production cost is minimum) is found to be 190 kt for regular pellet production and 250 kt for steam pretreated pellet. Sensitivity and uncertainty analyses were carried out to identify sensitivity parameters and effects of model error.     

Determining long-term chipper usage,productivity and fuel consumption

The Authors surveyed 6 industrial chipping operations for a whole work year, collecting data about machine usage, product output, fuel consumption and chipper knife wear. Despite the challenging work conditions offered by mountain operations, industrial chipping contractors manage to achieve a high machine use, ranging from 500 to over 2,500 h year⁻¹. Product output varies between 18,000 and over 120,000 m³ loose chips per year. In order to acquire enough jobs, operators may travel between 1,500 to over 20,000 km in a year. Industrial chipping contractors adopt different operational strategies to achieve their production targets, and they equip accordingly. Some operators prefer to tap smaller local areas and opt for smaller tractor-powered chippers, which are less powerful and productive than larger independent-engine units, but cheaper and capable of negotiating low-standard forest roads. Others prefer to explore larger areas and achieve higher product outputs, and they opt for larger independent-engine chippers, often mounted on trucks. Long term productivity varies with machine type: tractor-powered units produce between 40 and 50 m³ loose chips per hour, whereas larger independent-engine chippers produce between 60 and 90 m³ loose chips per hour. Specific fuel consumption is about 0.5 L diesel per m³ loose chips, regardless of chipper type. A sharp knife set can process between 200 and 1,500 m³ loose chips before getting dull. Disposable knives last longer and are cheaper to manage than standard re-usable knives.     

The economic potential of wood pellet production from alternative,low-value wood sources in the southeast of the U.S.

The global demand for wood pellets used for energy purposes is growing. Therefore, increased amounts of wood pellets are produced from primary forestry products, such as pulp wood. The present analysis demonstrates that substantial amounts of alternative, low-value wood resources are available that could be processed into wood pellets. For three resources, test batches have been produced and tested to qualify for industrial pellet standards. These include: primary forestry residues from premerchantable thinning operations, secondary forestry residues from pole mills and post-consumer wood wastes from discarded wooden transport pallets. The total wood potential of these resources in the southeast of the U.S. (Florida, Georgia, North Carolina, South Carolina), was estimated to be 1.9 Tg y⁻¹ (dry) available at roadside (excluding transport cost) for 22 $ Mg⁻¹ (dry) increasing to over 5.1 Tg y⁻¹ at 33 $ Mg⁻¹ (dry). In theory, 4.1 Tg y⁻¹ pellets could be produced from the estimated potential. However, due to the geographically dispersed supply of these resources, the cost of feedstock supply at a pellet plant increases rapidly at larger plants. It is therefore not expected that the total potential can be processed into wood pellets at costs competitive with those of conventional wood pellets. The optimal size of a pellet plant was estimated at between 55 Gg y⁻¹ and 315 Gg y⁻¹ pellets depending on the location and feedstock supply assumptions. At these locations and plant sizes, pellets could be produced at competitive costs of between 82 $ Mg⁻¹ and 100 $ Mg⁻¹ pellets.     

Evaluation of alternatives for the evolution of palm oil mills into biorefineries

Six alternatives for the conversion of an average Colombian palm oil mill (30 t h⁻¹ of fresh fruit bunches (FFB) into biorefineries were evaluated. The alternatives studied were: (C1) Production of biogas from the Palm Oil Mill Effluents (POME), (C2) Composting of empty fruit bunches (EFB) and fiber, (C3) Biomass combustion for high pressure steam combined heat and power, (C4) Pellets production, (C5) Biochar production and, (C6) Biochar and bio-oil production. The available biomass could result in up to 125 kWh of electricity, 207 kg of compost, 125 kg of pellet, 44 kg of biochar and 63 kg of bio-oil per metric ton of FFB. The global warming potential (GWP), eutrophication potential (EP), net energy ratio (NER), capital expenditures (CAPEX), operational costs (OPEX), net present value (NPV) and internal rate of return (IRR) were calculated for all the alternatives. GHG reductions of more than 33% could be achieved. Anaerobic digestion and composting contributed to 30% reduction of the EP. The CAPEX for all of the biorefinery alternatives studied varies between 0.7 $ t⁻¹ and 2.8 $ t⁻¹ of FFB. The OPEX varies between 1.6 $ t⁻¹ and 7.3 $ t⁻¹ of FFB. The NPV for viable scenarios ranged between 2.5 million and 13.9 million US dollars. The IRR calculated varied between 3% and 56% and the payback periods were between 3 and 8 years. The total extra incomes reached values up to 15.2 $ t⁻¹ of FFB. Overall the pellets production biorefinery was the preferred alternative.     

The economics of chipping logging residues at roadside: A study of three systems

Three biomass chipping operations of roadside logging residues were studied in New Brunswick and Maine. Two of the operations used a skidder-loader to form the roadside debris into larger piles closer to the road edge prior to chipping. Average chipping productivity ranged from 8.l oven dry Mg per Productive Machine Hour (OdMg PMH⁻¹) to 28.2 OdMg PMH⁻¹ depending on the site and chipping system used. The average cost of chips on board the chip vans ranged from $15.29 CAN OdMg⁻¹ to $25.86 CAN OdMg⁻¹. The chips were transported to three energy plants in Maine. One-way hauling distances varied from 29 km to 105 km.     

Technoeconomic analysis of jet fuel production from hydrolysis,decarboxylation, and reforming of camelina oil

The commercial production of jet fuel from camelina oil via hydrolysis, decarboxylation, and reforming was simulated. The refinery was modeled as being close to the farms for reduced camelina transport cost. A refinery with annual nameplate capacity of 76,000 cubic meters hydrocarbons was modeled. Assuming average camelina production conditions and oil extraction modeling from the literature, the cost of oil was 0.31 $ kg⁻¹. To accommodate one harvest per year, a refinery with 1 year oil storage capacity was designed, with the total refinery costing 283 million dollars in 2014 USD. Assuming co-products are sold at predicted values, the jet fuel break-even selling price was 0.80 $ kg⁻¹. The model presents baseline technoeconomic data that can be used for more comprehensive financial and risk modeling of camelina jet fuel production. Decarboxylation was compared to the commercially proven hydrotreating process. The model illustrated the importance of refinery location relative to farms and hydrogen production site.     

Potential for rice straw ethanol production in the Mekong Delta,Vietnam

This study is to evaluate the potential for development of a cellulosic ethanol facility in Vietnam. Rice straw is abundant in Vietnam and highly concentrated in the Mekong Delta, where about 26 Mt year⁻¹ of rice straw has been yearly produced. To minimize the overall production cost (PC) of ethanol from rice straw, it is crucial to choose the optimal facility size. The delivered cost of rice straw varied from 20.5 to 65.4 $ dry t⁻¹ depending on transportation distance. The Mekong Delta has much lower rice straw prices compared with other regions in Vietnam because of high density and quantity of rice straw supply. Thus, this region has been considered as the most suitable location for deploying ethanol production in Vietnam. The optimal plant size of ethanol production in the region was estimated up to 200 ML year⁻¹. The improvement in solid concentration of material in the hydrothermal pre-treatment step and using residues for power generation could substantially reduce the PC in Vietnam, where energy costs account for the second largest contribution to the PC, following only enzyme costs. The potential for building larger ethanol plants with low rice straw costs can reduce ethanol production costs in Vietnam. The current estimated production cost for an optimal plant size of 200 ML year⁻¹ was 1.19 $ L⁻¹. For the future scenario, considering improvements in pre-treatment, enzyme hydrolysis steps, specific enzyme activity, and applying residues for energy generation, the ethanol production cost could reduce to 0.45 $ L⁻¹ for a plant size of 200 ML year⁻¹ in Vietnam. These data indicated that the cost-competitiveness of ethanol production could be realized in Vietnam with future improvements in production technologies.     

Productivity and cost of mechanized energy wood harvesting in Northern Scotland

At present, the utilization of timber in the Northern part of the Scottish Highlands is low due to a lack of a wood utilizing industry. As a consequence, the majority of forest owners do not receive any income from timber and in some cases stumpage prices can even be negative. At the same time, increasing prices of oil, gas and electricity pose a great challenge for local industries and homeowners. The establishment of wood fueled heating systems is therefore expected to improve the situation and at the same time create a market for the local timber resources. Consequently, a local energy source to produce heat and electricity at a competitive price would have positive benefits for both local industries and forest owners. Due to the current lack of competition, roundwood could be chipped for fuel, which has many associated benefits compared to the harvesting and chipping of logging residues. It is the aim of this research to apply existing Finnish know-how in regards to wood fuel harvesting in order to develop and investigate the price level of sustainable and local wood fuel supply chains.To determine the most suitable supply chain for forest fuels, various research methods were applied. An estimation of the forest resources in the Wick area was the first step of the research. The different cost components of the supply chain such as cutting, forwarding and chipping were then calculated based on Finnish experiences and adapted to conditions in Northern Scotland. Detailed transportation distance calculations and cost of transportation were calculated using GIS tools.Of the various supply chain designs considered, chipping at the landing seems to be the most suitable option. Chipping the roundwood at a central terminal would also be feasible; however, a suitable site would have to be identified since chipping of the material at the heating plant is not an option. Calculations indicate that forest chips can be delivered starting from approximately 20 € MWh⁻¹ within a 50 km transportation distance when chipping is at roadside. If the transportation distance is 100 km wood chips could be delivered at approximately 23 € MWh⁻¹. Results from the GIS analysis indicate that a sufficient supply of raw material will be available in the future. According to these calculations forest fuels can be a competitive energy source for heat and electricity production in Northern Scotland.     

Cost estimates of post harvest forest biomass supply for Canada

This study estimates the potential physical amounts and financial costs of post-harvest forest residue biomass supply in Canada. The analyses incorporate the locations of harvest activities in Canada, the geographical variation of forest productivity patterns and the costs associated with the extraction and transportation of residue feedstock to bioenergy facilities. We estimated the availability of harvest residues within the extent of industrial forest management operations in Canadian forests. Our analyses focused on the extraction of biomass from roadside harvest residues that involve four major cost components: pre-piling and aggregation, loading, chipping and transportation. The estimates of residue extraction costs also included representation of basic ecological sustainability and technical accessibility constraints. Annual supply of harvestable residual biomass with these ecological sustainability constraints were estimated to be approximately 19.2–23.3 Tg_*year⁻¹ and 16.5–20.0 Tg_*year⁻¹ in scenarios that included both ecological and technical accessibility limitations. These estimates appear to be less than other similar studies, due to the higher level of spatial details on inventories and ecological and operational constraints in our analyses. The amount of residual biomass available in baseline scenarios at a supply cost of $60 ODT⁻¹ and $80 ODT⁻¹ were 1.08 and 1.38 Tg year⁻¹ and 7.82 and 10.14 Tg year⁻¹ respectively. Decreasing residue extraction costs by 35% increased the amount of residues available at a $60 ODT⁻¹ and $80 ODT⁻¹ supply price by ∼5.5–5.7 and ∼1.5–1.6 times respectively. The assessment methodology is generic and could be extended to examine residue supplies for specialized biomass markets such as lignocellulosic ethanol production.     

Transport and handling of forest energy bundles—advantages and problems

Bundling is a technology used to create a compressed and uniform handling unit from logging residues and other small size energy wood. The bundles may be handled and transported with the same equipment that is used for conventional roundwood. Bundles also offer other advantages such as “cool systems”, good storing characteristics etc. This study deals with some advantages and problems of transport and handling bundled small size energy wood as an alternative to chips.Transport cost, from stump to consumer, is calculated. Two types of material were included in the analysis: bundles and fuel chips.Transport alternatives included transports directly to consumer as well as transports of bundles via a terminal for drying and chipping, and then, in the form of fuel chips directly to consumer with a bulk cargo truck.The study shows that bundles (especially if dry) are cheaper to transport than fuel chips in road transport bins. The useful cargo space is the limiting factor for trucks when transporting dry material. Transport cost decreased until the moisture content reached the critical levels, below 40.9% for chips in road transport bins and below 44.7% for bundles on timber truck. However, there are also other advantages with a dryer material.Chipping cost is lowest in the terminal alternative and highest in the system with chipping loose logging residues in the stand. However, transport via terminal sharply increases the total costs, due to handling and increased transportation work, especially on shorter distances.Transport of uncovered bundles on conventional log trucks can be dangerous because of the risk for pieces of wood falling off. Bundles may also disintegrate during handling. The risk increases if the bundles are not reinforced with e.g. long tops and small trees, or if the strings are damaged during storing. Sisal strings deteriorate and lose their strength after a relatively short period. Thus, they are less suitable than strings of, e.g. polypropylene.Cost savings in transport and chipping indicate an allowed cost for bundling of approximately 4–5 Euro/MWh for short to medium transport distances, to be competitive to the chip alternative. Cost estimates of bundling and covering of stacks with paper indicate that the handling cost is about the same as for chips for short to medium transport distances. However, for longer transport distances and through other advantages such as possibilities for return transports, a dryer and more storable material, cooler systems etc. may increase acceptable bundling-cost substantially.     

Processing and sorting forest residues: Cost,productivity and managerial impacts

Feedstocks generated from processing forest residues have traditionally been considered as a low value product. The economic potential of these materials can be enhanced by emerging biomass conversion technologies, such as torrefaction, briquetting, and gasification; however, these systems require higher quality feedstock. The objective of this study was to determine the cost of processing and sorting forest residues to produce feedstock, so that the best comminution machines (i.e. chipper vs. grinder) could be used to better control feedstock size distribution. The tree tops left from sawlog processing and small-diameter trees were delimbed and separated from the slash pile. Three harvest units were selected and each unit was divided into three sub-treatment units (no-, moderate, and intensive sorting). Results showed that the cost of operations were higher for the sorted sub-units when compared to the non-sorted. The total cost of operation (felling to loading) for sawlogs was lowest at 40.81 $ m⁻³ in the nosorting treatment unit, followed by moderate (42.25 $ m⁻³) and intensive treatment unit (44.75 $ m⁻³). For biomass harvesting, the cost of operation (felling to delimbing and sorting) ranged from 27 to 29 $ oven dry metric ton⁻¹. The most expensive operational phase was primary transportation; therefore, cost of treating the forest residues had less impact on the overall cost. The cost increase (1150 $ ha⁻¹) of sorting forest residues could offset cost savings from avoided site preparation expenses (1100 $ ha⁻¹), provided that the forest residues were utilized.     

Efficiency of a compactor in wood chip volume reduction

The baling of freshly harvested wood chips was tested in an Orkel MP2000, a baling machine extensively used in agriculture and industry to densify residues. Wood chips from two different feedstocks: poplar (Populus x euroamericana) and black locust (Robinia pseudoacacia). Baling effected a volume reduction of 43% with respect to the loose bulk density of the piled chips. Each bale has an average mass of 638 kg, and the time consumption to produce one bale was typically 98 s – 122 s. Productivity then varied from 19.8 t h⁻¹ and 21.7 t h⁻¹ of the fresh (green) wood chips. Diesel fuel consumption ranged from 1.4 L t⁻¹ to 1.5 L t⁻¹ of fresh chip weight and represented about 12% of the production cost. The packaging cost is approximately 23 € t⁻¹ of fresh chips equivalent to a bale cost of 15 €. Comminuted wood pressed into bales could provide a valid solution in the use of conventional agricultural and forestry machines. In fact, the handling and transportation of bales can be performed by means of equipment normally used in other agro-forestry activities (front loaders of tractors). In addition, pressed woodchips in packaged bales with waterproof sheets also guarantees a useful storage technique with significant storage surface reduction relative to loose wood chips.     

Industrial sugar beets to biofuel: Field to fuel production system and cost estimates

Specialized varieties of sugar beets (Beta vulgaris L.) may be an eligible feedstock for advanced biofuel designation under the USA Energy Independence and Security Act of 2007. These non-food industrial beets could double ethanol production per hectare compared to alternative feedstocks. A mixed-integer mathematical programming model was constructed to determine the breakeven price of ethanol produced from industrial beets, and to determine the optimal size and biorefinery location. The model, based on limited field data, evaluates Southern Plains beet production in a 3-year crop rotation, and beet harvest, transportation, and processing. The optimal strategy depends critically on several assumptions including a just-in-time harvest and delivery system that remains to be tested in field trials. Based on a wet beet to ethanol conversion rate of 110 dm³ Mg⁻¹ and capital cost of 128 M$ for a 152 dam³ y⁻¹ biorefinery, the estimated breakeven ethanol price was 507 $ m⁻³. The average breakeven production cost of corn (Zea mays L.) grain ethanol ranged from 430 to 552 $ m⁻³ based on average net corn feedstock cost of 254 and 396 $ m⁻³ in 2014 and 2013, respectively. The estimated net beet ethanol delivered cost of 207 $ m⁻³ was lower than the average net corn feedstock cost of 254–396$ m⁻³ in 2013 and 2014. If for a mature industry, the cost to process beets was equal to the cost to process corn, the beet breakeven ethanol price would be $387 m^-3 (587 $ m⁻³ gasoline equivalent).     

Selected environmental impacts of the technical production of wood chips from poplar short rotation coppice on marginal land

The use of marginal land for Short Rotation Coppice (SRC) might contribute to a sustainable energy supply in future. We assessed the environmental impacts of common production chains for manufacturing wood chips from SRC with poplar, including all the processes necessary to produce and deliver chips to a plant gate in 50 km distance from the field site (“cradle-to-plant gate”).To do so, we carried out a Life Cycle Analysis (LCA) including upstream processes. Results showed clearly that the specific environmental impacts were mainly caused by the processes “harvesting” and “transport”. Using a cut-and-chip harvesting system with a forage harvester generated low impacts during harvesting because of its high productivity. Using a cut-and-storage harvesting system with a whole rod harvester, however, didn't require accompanying tractor-trailer units during harvesting and allowed storing stems before chipping thereby, reducing the moisture content to approximately 30%. Consequently, the transport to the plant caused significantly lower environmental impacts at the same distance (50 km) which lead to a better result when looking at the overall production chain (26 vs. 36 kg CO₂-eq Mg_dm⁻¹). Respective energy output to energy input ratios were 23:1 and 26:1.We also analysed the impacts of irrigation and fertigation as they might be options to increase biomass yield. Both treatments lead to considerably increased environmental impacts in all analysed categories which might be balanced only if the biomass yields increase substantially; an effect which could not be verified within the current study.     

Energy use pattern and sensitivity analysis of energy inputs and input costs for pear production in Iran

The purposes of this study were to determine energy use pattern and investigate the relationships between energy inputs and yield, cost inputs and income for pear production in the Tehran province of Iran. In this study, data were collected by administering a questionnaire in face-to-face interviews in the production year of 2009/2010. This article presents a comprehensive picture of the current status of energy consumption and some energy indices like energy ratio, energy productivity, specific energy, net energy and energy intensiveness. Results showed that the total energy input of 172,608.43 MJ ha⁻¹ was required for pear production. Among input energy sources, electricity energy with share of 78% of total input energy had the highest share. The energy use efficiency and energy productivity were found as 0.51 and 0.27 kg MJ⁻¹, respectively. To investigate the relationships between energy inputs and yield, cost inputs and income, Cobb–Douglas production function was selected as the best function. Sensitivity analysis of energy and cost inputs was carried out using the marginal physical productivity (MPP) technique. Economic analysis of pear production was carried out and total cost of pear production was obtained as 11,936.97 $ h⁻¹. Also the benefit to cost ratio was calculated as 3.11.     

Supply assessment of forest biomass – A bottom-up approach for Sweden

As there is increasing interest in the use of biomass for energy in Sweden, the potential availability and harvesting costs of forest roundwood, harvesting residues and stumps were estimated up to the year 2069 in 10-year intervals, using a high spatial resolution GIS. In each individual forest area, an average harvesting cost per forest assortment was estimated, based on the geographic and other properties of the area. Using cost structure and resource availability, marginal cost curves were constructed to allow analyses of the effects of changing market conditions and different policy frameworks. Based on geographically explicit data, the results indicated that the average harvesting costs would be 21–24 € m⁻³ for roundwood, depending on the type of harvesting and extraction operation. The corresponding cost estimate for harvesting residues was 23–25 € m⁻³ and 35 € m⁻³ for stumps. The harvesting cost estimates lie on the steeper part of the marginal cost curve, suggesting that increases in the supply of woody biomass can only occur at significantly higher harvesting costs. From a policy perspective, this suggests that subsidies aimed at reducing the harvesting costs will only have limited success in increasing the harvested volumes, given current technology. Therefore, for future development in the supply of forest assortments for energy generation, it is important to consider not only the supply potential, but also the integration of improvements in harvesting and transportation systems.     

Should straw/stover be turned into syndiesel or ethanol?

Straw and corn stover can be used to produce ethanol by enzymatic hydrolysis and fermentation, or syndiesel by oxygen gasification and Fischer Tropsch (FT) reaction. FT has a higher processing cost and a higher energy yield of liquid transportation fuel. We analyze the cost of produced liquid fuel as a function of the field cost of biomass. At 80 $ t^?1 (dry basis) a crossover point is reached. Below this value, the cost of producing energy as ethanol is lower; above this value, FT syndiesel is lower. However, the crossover point occurs at a very high field cost of biomass, more than 5.50 $ GJ^?1, and ethanol plants are less capital intense than FT and hence have a smaller economic size. For both reasons ethanol is likely to be the preferred processing alternative.