Is Use of Both Pulpwood and Logging Residues Instead of Only Logging Residues for Bioenergy Development a Viable Carbon Mitigation Strategy?

This study adopts an integrated life-cycle approach to assess overall carbon saving related with the utilization of wood pellets manufactured using pulpwood and logging residues for electricity generation. Carbon sequestered in wood products and wood present in landfills and avoided carbon emissions due to substitution of grid electricity with the electricity generated using wood pellets are considered part of overall carbon savings. Estimated value of overall carbon saving is compared with the overall carbon saving related to the current use of pulpwood and logging residues. The unit of analysis is a hectare of slash pine (Pinus elliottii) plantation in southern USA. All carbon flows are considered starting from forest management to the decay of wood products in landfills. Exponential decay function is used to ascertain carbon sequestered in wood products and wood present in landfills. Non-biogenic carbon emissions due to burning of wood waste at manufacturing facilities, wood pellets at a power plant, and logging residues on forestlands are also considered. Impacts of harvest age and forest management intensity on overall carbon saving are analyzed as well. The use of pulpwood for bioenergy development reduces carbon sequestered in wood products and wood present in landfills (up to 1.6 metric tons/ha) relative to a baseline when pulpwood is used for paper making and logging residues are used for manufacturing wood pellets. Avoided carbon emissions because of displacement of grid electricity from the electricity generated using wood pellets derived from pulpwood fully compensate the loss of carbon sequestered in wood products and wood present in landfills. The use of both pulpwood and logging residues for bioenergy development is beneficial from carbon perspective. Harvest age is more important in determining overall carbon saving than forest management intensity.     

Wood pellets,what else? Greenhouse gas parity times of European electricity from wood pellets produced in the south‐eastern United States using different softwood feedstocks

Several EU countries import wood pellets from the south‐eastern United States. The imported wood pellets are (co‐)fired in power plants with the aim of reducing overall greenhouse gas (GHG) emissions from electricity and meeting EU renewable energy targets. To assess whether GHG emissions are reduced and on what timescale, we construct the GHG balance of wood‐pellet electricity. This GHG balance consists of supply chain and combustion GHG emissions, carbon sequestration during biomass growth and avoided GHG emissions through replacing fossil electricity. We investigate wood pellets from four softwood feedstock types: small roundwood, commercial thinnings, harvest residues and mill residues. Per feedstock, the GHG balance of wood‐pellet electricity is compared against those of alternative scenarios. Alternative scenarios are combinations of alternative fates of the feedstock materials, such as in‐forest decomposition, or the production of paper or wood panels like oriented strand board (OSB). Alternative scenario composition depends on feedstock type and local demand for this feedstock. Results indicate that the GHG balance of wood‐pellet electricity equals that of alternative scenarios within 0–21 years (the GHG parity time), after which wood‐pellet electricity has sustained climate benefits. Parity times increase by a maximum of 12 years when varying key variables (emissions associated with paper and panels, soil carbon increase via feedstock decomposition, wood‐pellet electricity supply chain emissions) within maximum plausible ranges. Using commercial thinnings, harvest residues or mill residues as feedstock leads to the shortest GHG parity times (0–6 years) and fastest GHG benefits from wood‐pellet electricity. We find shorter GHG parity times than previous studies, for we use a novel approach that differentiates feedstocks and considers alternative scenarios based on (combinations of) alternative feedstock fates, rather than on alternative land uses. This novel approach is relevant for bioenergy derived from low‐value feedstocks.     

Tracking Economic and Environmental Indicators of Exported Wood Pellets to the United Kingdom from the Southern United States: Lessons for Policy?

This study estimates the abatement cost of greenhouse gas (GHG) emissions for a unit of electricity generated in the UK from wood pellets imported from Southern USA. We assumed that only pulpwood obtained from loblolly pine (Pinus taeda) plantations was used for manufacturing exported wood pellets. The use of imported wood pellets for electricity generation could save at least 69.9 % of GHG emissions relative to coal-based electricity in the UK. The average unit production cost of electricity generated from imported wood pellets (US$222.3 MWh^?1) was higher by 30.0 % than the unit production cost of electricity generated from coal (US$171.0 MWh^?1) without any price support. In the presence of payments from the established price support mechanisms of Renewable Obligation Certificates (ROCs) and Levy Exemption Certificates (LECs), the unit production cost of electricity generated from imported wood pellets (US$142.9 MWh^?1) was lower by about 16.0 % than the unit production cost of electricity generated from coal. Policy makers should consider 1 MWh of electricity generated from imported wood pellets equivalent to 0.58 ROCs or 0.71 ROCs in presence and absence of payments from LECs, respectively. This will ensure zero abatement cost and lead to economic efficiency in reducing GHG emissions. However, a more in-depth analysis focusing on the market risks for power-generating companies and other wood pellet supply chains is required before modifying existing equivalency factors for ensuring continuous use of imported wood pellets for displacing coal-based electricity in the UK.     

Quantifying GWI of Wood Pellet Production in the Southern United States and Its Subsequent Utilization for Electricity Production in The Netherlands/Florida

This study attempts to determine global warming impact (GWI) of imported wood pellets from the Southern United States for electricity production in The Netherlands. An attempt is also made to determine GWI of utilizing produced wood pellets within the state of Florida for electricity generation instead of exports. A life-cycle approach is adopted to determine overall GWIs of both the cases. Economic objectives of forest landowners are also incorporated to determine biomass (pulpwood and harvesting residues) availability from a hectare of slash pine plantation. The GWI of a unit of electricity produced at a power plant located at Geertruidenberg, The Netherlands and Gainesville, Florida was 296.4 and 177.5 g of carbon dioxide equivalent greenhouse gas, respectively. An overall saving of 72.6% in greenhouse gas emissions was estimated for every kilowatt-hour of electricity generated using imported wood pellets in The Netherlands when compared with coal-based electricity. This value was found to be 82.4% if produced wood pellets are utilized within Florida for electricity generation instead of exports. A need exists to evaluate the potential of other feedstocks for wood pellet production like understory forest biomass. Additionally, macroeconomic and ecological impacts of utilizing forest biomass for wood pellet production needs to be quantified.     

An assessment of biomass for bioelectricity and biofuel,and for greenhouse gas emission reduction in Australia

We provide a quantitative assessment of the prospects for current and future biomass feedstocks for bioenergy in Australia, and associated estimates of the greenhouse gas (GHG) mitigation resulting from their use for production of biofuels or bioelectricity. National statistics were used to estimate current annual production from agricultural and forest production systems. Crop residues were estimated from grain production and harvest index. Wood production statistics and spatial modelling of forest growth were used to estimate quantities of pulpwood, in‐forest residues, and wood processing residues. Possible new production systems for oil from algae and the oil‐seed tree Pongamia pinnata, and of lignocellulosic biomass production from short‐rotation coppiced eucalypt crops were also examined. The following constraints were applied to biomass production and use: avoiding clearing of native vegetation; minimizing impacts on domestic food security; retaining a portion of agricultural and forest residues to protect soil; and minimizing the impact on local processing industries by diverting only the export fraction of grains or pulpwood to bioenergy. We estimated that it would be physically possible to produce 9.6 GL yr^?1 of first generation ethanol from current production systems, replacing 6.5 GL yr^?1 of gasoline or 34% of current gasoline usage. Current production systems for waste oil, tallow and canola seed could produce 0.9 GL yr^?1 of biodiesel, or 4% of current diesel usage. Cellulosic biomass from current agricultural and forestry production systems (including biomass from hardwood plantations maturing by 2030) could produce 9.5 GL yr^?1 of ethanol, replacing 6.4 GL yr^?1 of gasoline, or ca. 34% of current consumption. The same lignocellulosic sources could instead provide 35 TWh yr^?1, or ca. 15% of current electricity production. New production systems using algae and P. pinnata could produce ca. 3.96 and 0.9 GL biodiesel yr^?1, respectively. In combination, they could replace 4.2 GL yr^?1 of fossil diesel, or 23% of current usage. Short‐rotation coppiced eucalypt crops could provide 4.3 GL yr^?1 of ethanol (2.9 GL yr^?1 replacement, or 15% of current gasoline use) or 20.2 TWh yr^?1 of electricity (9% of current generation). In total, first and second generation fuels from current and new production systems could mitigate 26 Mt CO₂‐e, which is 38% of road transport emissions and 5% of the national emissions. Second generation fuels from current and new production systems could mitigate 13 Mt CO₂‐e, which is 19% of road transport emissions and 2.4% of the national emissions lignocellulose from current and new production systems could mitigate 48 Mt CO₂‐e, which is 28% of electricity emissions and 9% of the national emissions. There are challenging sustainability issues to consider in the production of large amounts of feedstock for bioenergy in Australia. Bioenergy production can have either positive or negative impacts. Although only the export fraction of grains and sugar was used to estimate first generation biofuels so that domestic food security was not affected, it would have an impact on food supply elsewhere. Environmental impacts on soil, water and biodiversity can be significant because of the large land base involved, and the likely use of intensive harvest regimes. These require careful management. Social impacts could be significant if there were to be large‐scale change in land use or management. In addition, although the economic considerations of feedstock production were not covered in this article, they will be the ultimate drivers of industry development. They are uncertain and are highly dependent on government policies (e.g. the price on carbon, GHG mitigation and renewable energy targets, mandates for renewable fuels), the price of fossil oil, and the scale of the industry.     

Optimal configuration and combination of multiple lignocellulosic biomass feedstocks delivery to a biorefinery

Biomass availability and transportation are major challenges in establishing a large-scale biorefinery. The objective of this study was to assess the delivery cost of different combinations of multiple forms of lignocellulosic feedstocks including agricultural and woody biomass. Three types of biomass i.e., wheat straw, corn stover and forest biomass were considered in different forms such as loose biomass, bales/bundles, chopped/chipped and pellets. It was found that the delivery cost of a combination of woody and agricultural biomass feedstocks is lower than that for a single type of biomass. The delivery of agricultural residues as bales and woody biomass as chips is an economically attractive option with optimal combination of 30% bales and 70% wood chips to a biorefinery of capacity 5000 dry tonnes per day. The anticipated traffic congestions resulting from biomass supply to a large facility could be significantly reduced by increasing the density of biomass.     

Time-Dependent Climate Impact and Energy Efficiency of Internationally Traded Non-torrefied and Torrefied Wood Pellets from Logging Residues

Demand for wood pellets as a renewable alternative to fossil fuels has increased in the past decade. However, production and use of wood pellets involves several operations (biomass extraction, chipping, transport, drying, milling, pelleting, combustion) with negative impacts on e.g. the climate. In this study, the energy efficiency and climate impact of production and use of non-torrefied and torrefied wood pellets were analysed and compared. The wood pellets, produced from logging residues extracted from a boreal coniferous forest stand (Norway spruce (Picea abies (L.) H. Karst)) in northern Sweden, were assumed to be exported and finally used in a power plant. Time-dependent life cycle assessment, expressing the climate impact as global temperature change over time, was used to include annual greenhouse gas fluxes of both fossil and biogenic origin. The results showed that carbon stock changes due to extraction of logging residues contributed most of the warming effect on global temperature. Due to greater demand for raw material, a higher warming impact per gigajoule fuel was obtained for torrefied wood pellets than for non-torrefied wood pellets. However, torrefied wood pellets demonstrated a lower climate impact (per GJ electricity) when advantages such as higher electrical energy efficiency and higher co-firing rate were included. A general conclusion from this study is that replacing coal with non-torrefied or torrefied wood pellets made from logging residues can mitigate climate change. The energy output of these systems was about sevenfold the primary energy input.     

Life Cycle Assessment of End‐of‐Life Management Options for Construction and Demolition Debris

A life cycle assessment (LCA) of various end‐of‐life management options for construction and demolition (C&D) debris was conducted using the U.S. Environmental Protection Agency's Municipal Solid Waste Decision Support Tool. A comparative LCA evaluated seven different management scenarios using the annual production of C&D debris in New Hampshire as the functional unit. Each scenario encompassed C&D debris transport, processing, separation, and recycling, as well as varying end‐of‐life management options for the C&D debris (e.g., combustion to generate electricity versus landfilling for the wood debris stream and recycling versus landfilling for the nonwood debris stream) and different bases for the electricity generation offsets (e.g., the northeastern U.S. power grid versus coal‐fired power generation). A sensitivity analysis was also conducted by varying the energy content of the C&D wood debris and by examining the impact of basing the energy offsets on electricity generated from various fossil fuels. The results include impacts for greenhouse gas (GHG) emissions, criteria air pollutants, ancillary solid waste production, and organic and inorganic constituents in water emissions. Scenarios with nonwood C&D debris recycling coupled with combustion of C&D wood debris to generate electricity had lower impacts than other scenarios. The nonwood C&D debris recycling scenarios where C&D wood debris was landfilled resulted in less overall impact than the scenarios where all C&D debris was landfilled. The lowest impact scenario included nonwood C&D debris recycling with local combustion of the C&D wood debris to generate electricity, providing a net gain in energy production of more than 7 trillion British thermal units (BTU) per year and a 130,000 tons per year reduction in GHG emissions. The sensitivity analysis revealed that for energy consumption, the model is sensitive to the energy content of the C&D wood debris but insensitive to the basis for the energy offset, and the opposite is true for GHG emissions.     

Implications of emissions timing on the cost‐effectiveness of greenhouse gas mitigation strategies: application to forest bioenergy systems

Conventional cost‐effectiveness calculations ignore the implications of greenhouse gas (GHG) emissions timing and thus may not properly inform decision‐makers in the efficient allocation of resources to mitigate climate change. To begin to address this disconnect with climate change science, we modify the conventional cost‐effectiveness approach to account for emissions timing. GHG emissions flows occurring over time are translated into an ‘Equivalent Present Emission’ based on radiative forcing, enabling a comparison of system costs and emissions on a consistent present time basis. We apply this ‘Present Cost‐Effectiveness’ method to case studies of biomass‐based electricity generation (biomass co‐firing with coal, biomass cogeneration) to evaluate implications of forest carbon trade‐offs on the cost‐effectiveness of emission reductions. Bioenergy production from forest biomass can reduce forest carbon stocks, an immediate emissions source that contributes to atmospheric greenhouse gases. Forest carbon impacts thereby lessen emission reductions in the near‐term relative to the assumption of biomass ‘carbon neutrality’, resulting in higher costs of emission reductions when emissions timing is considered. In contrast, conventional cost‐effectiveness approaches implicitly evaluate strategies over an infinite analytical time horizon, underestimating nearer term emissions reduction costs and failing to identify pathways that can most efficiently contribute to climate change mitigation objectives over shorter time spans (e.g. up to 100 years). While providing only a simple representation of the climate change implications of emissions timing, the Present Cost‐Effectiveness method provides a straightforward approach to assessing the cost‐effectiveness of emission reductions associated with any climate change mitigation strategy where future GHG reductions require significant initial capital investment or increase near‐term emissions. Timing is a critical factor in determining the attractiveness of any investment; accounting for emissions timing can better inform decisions related to the merit of alternative resource uses to meet near‐, mid‐, and long‐term climate change mitigation objectives.     

Environmental impacts of bioenergy wood production from poplar short‐rotation coppice grown at a marginal agricultural site in Germany

For avoiding competition with food production, marginal land is economically and environmentally highly attractive for biomass production with short‐rotation coppices (SRCs) of fast‐growing tree species such as poplars. Herein, we evaluated the environmental impacts of technological, agronomic, and environmental aspects of bioenergy production from hybrid poplar SRC cultivation on marginal land in southern Germany. For this purpose, different management regimes were considered within a 21‐year lifetime (combining measurements and modeling approaches) by means of a holistic Life Cycle Assessment (LCA). We analyzed two coppicing rotation lengths (7 × 3 and 3 × 7 years) and seven nitrogen fertilization rates and included all processes starting from site preparation, planting and coppicing, wood chipping, and heat production up to final stump removal. The 7‐year rotation cycles clearly resulted in higher biomass yields and reduced environmental impacts such as nitrate (NO₃) leaching and soil nitrous oxide (N₂O) emissions. Fertilization rates were positively related to enhanced biomass accumulation, but these benefits did not counterbalance the negative impacts on the environment due to increased nitrate leaching and N₂O emissions. Greenhouse gas (GHG) emissions associated with the heat production from poplar SRC on marginal land ranged between 8 and 46 kg CO₂‐eq. GJ^?1 (or 11–57 Mg CO₂‐eq. ha^?1). However, if the produced wood chips substitute oil heating, up to 123 Mg CO₂‐eq. ha^?1 can be saved, if produced in a 7‐year rotation without fertilization. Dissecting the entire bioenergy production chain, our study shows that environmental impacts occurred mainly during combustion and storage of wood chips, while technological aspects of establishment, harvesting, and transportation played a negligible role.     

Economic Assessment of Greenhouse Gas Emissions Reduction by Vehicle Lightweighting Using Aluminum and High‐Strength Steel

The life cycle greenhouse gas (GHG) reduction benefits of vehicle lightweighting (LW) were evaluated in a companion article. This article provides an economic assessment of vehicle LW with aluminum and high‐strength steel. Relevant cost information taken from the literature is synthesized, compiled, and formed into estimates of GHG reduction costs through LW. GHG emissions associated with vehicle LW scenarios between 6% and 23% are analyzed alongside vehicle life cycle costs to achieve these LW levels. We use this information to estimate the cost to remove GHG emissions per metric ton by LW, and we further calculate the difference between added manufacturing cost and fuel cost savings from LW. The results show greater GHG savings derived from greater LW and added manufacturing costs as expected. The associated production costs are, however, disproportionately higher than the fuel cost savings associated with higher LW options. A sensitivity analysis of different vehicle classes confirms that vehicle LW is more cost‐effective for larger vehicles. Also, the cost of GHG emissions reductions through lightweighting is compared with alternative GHG emissions reduction technologies for passenger vehicles, such as diesel, hybrid, and plug‐in hybrid electric powertrains. The results find intensive LW to be a competitive and complementary approach relative to the technological alternatives within the automotive industry but more costly than GHG mitigation strategies available to other industries.     

Life cycle assessment of renewable diesel production from lignocellulosic biomass

Purpose

Governments around the world encourage the use of biofuels through fuel standard policies that require the addition of renewable diesel in diesel fuel from fossil fuels. Environmental impact studies of the conversion of biomass to renewable diesel have been conducted, and life cycle assessments (LCA) of the conversion of lignocellulosic biomass to hydrogenation-derived renewable diesel (HDRD) are limited, especially for countries with cold climates like Canada.

Methods

In this study, an LCA was conducted on converting lignocellulosic biomass to HDRD by estimating the well-to-wheel greenhouse gas (GHG) emissions and fossil fuel energy input of the production of biomass and its conversion to HDRD. The approach to conduct this LCA includes defining the goal and scope, compiling a life cycle inventory, conducting a life cycle impact assessment, and executing a life cycle interpretation. All GHG emissions and fossil fuel energy inputs were based on a fast pyrolysis plant capacity of 2000 dry tonnes biomass/day. A functional unit of 1 MJ of HDRD produced was adopted as a common unit for data inputs of the life cycle inventory. To interpret the results, a sensitivity analysis was performed to measure the impact of variables involved, and an uncertainty analysis was performed to assess the confidence of the results.

Results and discussion

The GHG emissions of three feedstocks studied—whole tree (i.e., chips from cutting the whole tree), forest residues (i.e., chips from branches and tops generated from logging operations), and agricultural residues (i.e., straw from wheat and barley)—range from 35.4 to 42.3 g CO_2,eq/MJ of HDRD (i.e., lowest for agricultural residue- and highest for forest residue-based HDRD); this is 53.4–61.1 % lower than fossil-based diesel. The net energy ratios range from 1.55 to 1.90 MJ/MJ (i.e., lowest for forest residue- and highest for agricultural residue-based HDRD) for HDRD production. The difference in results among feedstocks is due to differing energy requirements to harvest and pretreat biomass. The energy-intensive hydroprocessing stage is responsible for most of the GHG emissions produced for the entire conversion pathway.

Conclusions

Comparing feedstocks showed the significance of the efficiency in the equipment used and the physical properties of biomass in the production of HDRD. The overall results show the importance of efficiency at the hydroprocessing stage. These findings indicate significant GHG mitigation benefits for the oil refining industry using available lignocellulosic biomass to produce HDRD for transportation fuel.

     

A life cycle evaluation of wood pellet gasification for district heating in British Columbia

The replacement of natural gas combustion for district heating by wood waste and wood pellets gasification systems with or without emission control has been investigated by a streamlined LCA. While stack emissions from controlled gasification systems are lower than the applicable regulations, compared to the current base case, 12% and 133% increases are expected in the overall human health impacts for wood pellets and wood waste, respectively. With controlled gasification, external costs and GHG emission can be reduced by 35% and 82% on average, respectively. Between wood pellets and wood waste, wood pellets appear to be the better choice as it requires less primary energy and has a much lower impact on the local air quality.     

Life cycle assessment of eucalyptus short rotation coppices for bioenergy production in southern France

Short rotation coppices (SRC) are considered prime candidates for biomass production, yielding good‐quality feedstock that is easy to harvest. Besides technical, social and economical aspects, environmental issues are important to be taken into account when developing SRC. Here, we evaluated the environmental impacts of delivering 1 GJ of heat from eucalyptus SRC using life cycle assessment (LCA), based on management scenarios involving different rotations lengths, fertilizer input rates, stem densities and harvest methods. Compared to equivalent fossil chains, all eucalyptus scenarios achieved savings of fossil energy and greenhouse gas (GHG) emissions in the 80–90% range, and had generally lower impacts, except for eutrophication. The 3 year rotation scenario was the most energy and GHG‐intensive, whereas manual felling for the longer rotations resulted in twofold larger photochemical ozone impacts compared to the other scenarios. Transportation of wood chips and fertilization were the top two contributors to the impacts, the latter being more important with the shorter rotation lengths due to the evergreen character of eucalyptus. The possibility of including ecosystem carbon dynamics was also investigated, by translating the temporary sequestration of atmospheric CO₂ in the above and belowground biomass of eucalyptus as CO₂ savings using various published equivalence factors. This offset the life cycle GHG emissions of heat provision from eucalyptus SRC by 70–400%.     

Policy Implications of Allocation Methods in the Life Cycle Analysis of Integrated Corn and Corn Stover Ethanol Production

A biorefinery may produce multiple fuels from more than one feedstock. The ability of these fuels to qualify as one of the four types of biofuels under the US Renewable Fuel Standard and to achieve a low carbon intensity score under California’s Low Carbon Fuel Standard can be strongly influenced by the approach taken to their life cycle analysis (LCA). For example, in facilities that may co-produce corn grain and corn stover ethanol, the ethanol production processes can share the combined heat and power (CHP) that is produced from the lignin and liquid residues from stover ethanol production. We examine different LCA approaches to corn grain and stover ethanol production considering different approaches to CHP treatment. In the baseline scenario, CHP meets the energy demands of stover ethanol production first, with additional heat and electricity generated sent to grain ethanol production. The resulting greenhouse gas (GHG) emissions for grain and stover ethanol are 57 and 25 g-CO₂eq/MJ, respectively, corresponding to a 40 and 74 % reduction compared to the GHG emissions of gasoline. We illustrate that emissions depend on allocation of burdens of CHP production and corn farming, along with the facility capacities. Co-product handling techniques can strongly influence LCA results and should therefore be transparently documented.     

Economic and greenhouse gas costs of Miscanthus supply chains in the United Kingdom

Miscanthus has been identified as one of the most promising perennial grasses for renewable energy generation in Europe and the United States [Mitigation and Adaptation Strategies for Global Change 9 (2004) 433]. However, the decision to use Miscanthus depends to a considerable degree on its economic and environmental performance [Soil Use and Management 24 (2008) 235; Renewable and Sustainable Energy Reviews 13 (2009) 1230]. This article assessed the spatial distribution of the economic and greenhouse gas (GHG) costs of producing and supplying Miscanthus in the UK. The average farm‐gate production cost of Miscanthus in the UK is estimated to be 40 £ per oven‐dried tonne (£ odt^?1), and the average GHG emissions from the production of Miscanthus are 1.72 kg carbon equivalent per oven‐dried tonnes per year (kg CE odt^?1 yr^?1). The production cost of Miscanthus varies from 35 to 55 £ odt^?1 with the lowest production costs in England, Wales and Northern Ireland, and the highest costs in Scotland. Sensitivity analysis shows that yield of Miscanthus is the most influential factor in its production cost, with precipitation the most crucial input in determining yield. GHG emissions from the production of Miscanthus range from 1.24 to 2.11 kg CE odt^?1 yr^?1. To maximize the GHG benefit, Miscanthus should be established preferentially on croplands, though other considerations obviously arise concerning suitability and value of the land for food production.     

Greenhouse gas emissions from forestry in East Norway

Purpose

So far no calculations have been made for greenhouse gas (GHG) emissions from forestry in East Norway. This region stands for 80 % of the Norwegian timber production. The aim of this study was to assess the annual GHG emissions of Norwegian forestry in the eastern parts of the country from seed production to final felling and transport of timber to sawmill and wood processing industry (cradle-to-gate inventory), based on specific Norwegian data.

Methods

The life cycle inventory was conducted with SimaPro applying primary and secondary data from Norwegian forestry. GHG emissions of fossil-related inputs from the technosphere were calculated for the functional unit of 1 m³ timber extracted and delivered to industry gate in East Norway in 2010. The analysis includes seed and seedling production, silvicultural operations, forest road construction and upgrading, thinning, final felling, timber forwarding and timber transport on road and rail from the forest to the industry. Norwegian time studies of forestry machines and operations were used to calculate efficiency, fuel consumption and transport distances. Due to the lack of specific Norwegian data in Ecoinvent, we designed and constructed unit processes based on primary and secondary data from forestry in East Norway.

Results and discussion

GHG emissions from forestry in East Norway amounted to 17.893 kg CO₂-equivalents per m³ of timber delivered to industry gate in 2010. Road transport of timber accounted for almost half of the total GHG emissions, final felling and forwarding for nearly one third of the GHG emissions. Due to longer road transport distances, pulpwood had higher impact on the climate change category than saw timber. The construction of forest roads had the highest impact on the natural land transformation category. The net CO₂ emissions of fossil CO₂ corresponded to 2.3 % of the CO₂ sequestered by 1 m³ of growing forest trees and were compared to a calculation of biogenic CO₂ release from the forest floor as a direct consequence of harvesting.

Conclusions

Shorter forwarding and road transport distances, increased logging truck size and higher proportion of railway transport may result in lower emissions per volume of transported timber. A life cycle assessment of forestry may also consider impacts on environmental categories other than climate change. Biogenic CO₂ emissions from the soil may be up to 10 times higher than the fossil-related emissions, at least in a short-term perspective, and are highly dependent on stand rotation length.     

Carbon debt repayment or carbon sequestration parity? Lessons from a forest bioenergy case study in Ontario,Canada

Forest bioenergy can contribute to climate change mitigation by reducing greenhouse gas (GHG) emissions associated with energy production. We assessed changes in GHG emissions resulting from displacement of coal with wood pellets for the Atikokan Generating Station located in Northwestern Ontario, Canada. Two contrasting biomass sources were considered for continuous wood pellet production: harvest residue from current harvest operations (residue scenario) and fibre from expanded harvest of standing live trees (stemwood scenario). For the stemwood scenario, two metrics were used to assess the effects of displacing coal with forest biomass on GHG emissions: (i) time to carbon sequestration parity, defined as the time from the beginning of harvest to when the combined GHG benefit of displacing coal with biomass and the amount of carbon in regenerating forest equalled the amount of forest carbon without harvest for energy production; and (ii) time to carbon debt repayment, defined as the time from the beginning of harvest to when the combined GHG benefit of displacing coal with biomass and the amount of carbon in the regenerating forest equalled forest carbon at the time of harvest. Only time to carbon sequestration parity was used for the residue scenario. In the residue scenario, carbon sequestration parity was achieved within 1 year. In the stemwood scenario, times to carbon sequestration parity and carbon debt repayment were 91 and 112 years, respectively. Sensitivity analysis showed that estimates were robust when parameter values were varied. Modelling experiments showed that increasing growth rates for regenerating stands in the stemwood scenario could substantially reduce time to carbon sequestration parity. We discuss the use of the two metrics (time to carbon sequestration parity and time to carbon debt repayment) for assessing the effects of forest bioenergy projects on GHG emissions and make recommendations on terminology and methodologies for forest bioenergy studies.     

Impacts of Intensive Management and Landscape Structure on Timber and Energy Wood Production and net CO2 Emissions from Energy Wood Use of Norway Spruce

The aim of this study was to analyze the effects of intensive management and forest landscape structure (in terms of age class distribution) on timber and energy wood production (m³?ha^?1), net present value (NPV, ? ha^?1) with implications on net CO₂ emissions (kg CO₂ MWh^?1 per energy unit) from energy wood use of Norway spruce grown on medium to fertile sites. This study employed simulations using a forest ecosystem model and the Emission Calculation Tool, considering in its analyses: timber (saw logs, pulp) and energy wood (small-sized stem wood and/or logging residuals for top part of stem, branches, and needles) from the first thinning and harvesting residuals and stumps from the final felling. At the stand level, both fertilization and high pre-commercial stand density clearly increased timber production and the amount of energy wood. Short rotation length (40 and 60?years) outputted, on average, the highest annual stem wood production (most fertile and medium fertile sites), the 60?year rotation also outputted the highest average annual net present value (NPV with interest rates of 1?C4%). On the other hand, even longer rotation lengths, up to 80 and 100?years, were needed to output the lowest net CO₂ emissions per year in energy wood use. At the landscape level, the largest productivity (both for timber and energy wood) was obtained using rotation lengths of 60 and 80?years with an initial forest landscape structure dominated by older mature stands (a right-skewed age-class distribution). If the rotation length was 120?years, the initial forest landscape dominated by young stands (a left-skewed age-class distribution) provided the highest productivity. However, the NPV with interest rate of 2% was, on average, the highest with a right-skewed distribution regardless of the rotation length. If the rotation length was 120?years, normal age class distribution provided, on average, the highest NPV. On the other hand, the lowest emissions (kg CO₂ MWh^?1a^?1) were obtained with the left-skewed age-class distribution using the rotation lengths of 60 and 80?years, and with the normal age-class distribution using the rotation length of 120?years. Altogether, the management regimes integrating both timber and energy wood production and using fertilization provided, on average, the lowest emissions over all management alternatives considered.     

An environmental and economic analysis of the wood-pellet chain: two case studies in Southern Italy

Purpose

Wood pellet heating systems are considered as an essential component of European plans to reduce greenhouse gas (GHG) emissions. The goal of this analysis was to estimate and compare the environmental impacts and the costs of the production of packed wood pellets. Two pellet production systems, using roundwood logs (case 1) and mainly sawdust (case 2), have been analysed in 2015 in Basilicata region (Southern Italy).

Methods

A life cycle assessment (LCA) analysis was applied to calculate the environmental impact indicators of each system, whilst a life cycle cost (LCC) analysis was implemented to evaluate the pellets’ cost production. Hence, the functional unit chosen was 1 t of produced pellets. The system boundaries considered for the purpose of the current investigation were from the tree felling to the pellet packaging. In particular, the following activities were considered: motor-manual felling and delimbing with a chainsaw, timber yarding with a tractor along the forest track, loading and transportation of the logs to the collection point, transportation of timber to the factories for a distance of 35 km, pellet production and pellet packaging in low-density polyethylene bags with a total weight of 15 kg bag^?1.

Results and discussion

The production of 1 t of pellets emitted about 83 kg of CO₂eq in case 1 and 38 kg in case 2. In addition, 2.7 kg of SO₂eq and 0.005 kg of PO³ ₄-eq were produced in case 1 and 1.4 kg of SO₂eq and 0.002 kg of PO³ ₄-eq in case 2. Mineral extraction was equal to 0.9 MJ surplus energy in both cases. Case 1 led to higher environmental impacts (about 50% more), essentially for the operation of pelletisation, and in particular for the higher consumption of electricity that characterised it, whereas the production costs were 172 and 113 € t^?1 in case 1 and case 2, respectively. In both study cases, consumption costs (costs for raw material, electricity consumption, fuel usage) were the most important cost items.

Conclusions

Our studies highlight how, in both cases, the operations carried out in the forest produced the minor part of the environmental impact but, at the same time, were the most expensive operations. Further, our studies show how mixing lumbering by-products (sawdust) and forest management products (lumbers) can be an efficient solution to reduce both manufacturing costs and environmental impacts to produce wood pellets.