Pål Börjesson

Energy analysis of biomass production and transportation.

Energy efficiency in the production and transportation of different kinds of biomass in Sweden has been analysed, as well as the change in energy efficiency in a transition from fossil-fuel-based to biomass-based systems. Net energy yields under current production conditions were found to be highest for short-rotation forest (Salix) and sugar beet (about 160 to 170 GJ ha-1 year-1), followed by ley crops (110 to 140 GJ ha-1 year-1), and rape, wheat, and potatoes (50 to 90 GJ ha-1 year-1). The energy input per unit biomass produced is lowest for straw, logging residues and Salix, equal to 4 to 5% of the energy output. Corresponding figures for perennial ley crops are 7 to 10% and for annual crops 15 to 35%. Salix chips can be transported by truck about 250 km before the transportation energ is equal to the production energy. Corresponding distances for tractor, train and boat (coastal shipping) are about 100 km, 500 km and 1000 km, respectively. It is estimated that future increases in yield and technological development will almost double net energy yields for dedicated energy crops within the next two decades. A transition from a fossil-fuel-based energy system to a CO2-neutral biomass-based system around the year 2015 is estimated to increase the energy input in biomass production and transportation by about 30 to 45%, resulting in a decreased net energy output of about 4%. (Less)

Greenhouse gas balances in building construction: wood versus concrete from life-cycle and forest land-use perspectives

Greenhouse Gas Balances in Building Construction : Wood versus Concrete from Lifecycle and Forest Land-Use Perspectives

Environmental effects of energy crop cultivation in Sweden—I: Identification and quantification

This paper presents an analysis of how energy crop cultivations in Sweden, consisting of short-rotation forest (Salix) and energy grass (reed canary grass), can be located and managed to maximise environmental benefits. The overall conclusion is that substantial environmental benefits, ranging from global to site-specific, could be achieved when traditional annual food crops produced with current agriculture practices are replaced by dedicated perennial energy crops. The emission of greenhouse gases could be reduced by reduced carbon dioxide emissions from organic soils, by reduced nitrous oxide emissions caused by the use of fertilisers and through accumulation of soil carbon in mineral soils, which also leads to increased soil fertility. Nutrient leaching could be reduced by using energy crop cultivations as buffer strips along open streams and wind erosion could be reduced by using Salix plantations as shelter belts. Cultivation of Salix and energy grass can also be used to purify municipal waste, such as waste water, landfill leachate, and sewage sludge. Furthermore, the content of heavy metals in the soil can be reduced through Salix cultivation. The biodiversity is estimated to be almost unchanged, or slightly increased in open farmland. These environmental benefits, which could be achieved on up to 60% of current Swedish arable land and last for 25 years or more, will increase the value of the energy crops. The economic value of these benefits is calculated in Part II of the analysis, which is presented in a second paper.

REDUCING CO2 EMISSIONS BY SUBSTITUTING BIOMASS FOR FOSSIL FUELS

Replacing fossil fuels with sustainably-produced biomass will reduce the net flow of CO2 to the atmosphere. We express the efficiency of this substitution in reduced emissions per unit of used land or biomass and in costs of the substitution per tonne of C. The substitution costs are calculated as the cost difference between continued use of fossil fuels at current prices and the use of biomass, assuming that the biomass technologies are implemented when reinvestments in existing technologies are required. Energy inputs into biomass production and conversion are biomass-based, resulting in a CO2-neutral fuel cycle, while CO2 emissions from fossil fuels are estimated for the complete fuel cycles. Substituting biomass for fossil fuels in electricity and heat production is, in general, less costly and provides larger CO2 reduction per unit of biomass than substituting biomass for gasoline or diesel used in vehicles. For transportation, methanol or ethanol produced from short-rotation forests or logging residues provide larger CO2-emission reductions than rape methyl ester from rape seed, biogas from lucerne (alfalfa), or ethanol from wheat. Of these, methanol has the lowest emission-reduction costs. Increasing biomass used by 125 TWh/yr, the estimated potential for increased utilization of logging residues, straw and energy crops, would eliminate more than one-half of the Swedish CO2 emissions from fossil fuels of 15 Mtonnes C in 1992.

Regional production and utilization of biomass in Sweden

Regional production and utilization of biomass in Sweden is analysed, considering the potential of replacing fossil fuels and producing new electricity. Extensive utilization of biomass will decrease biomass-transportation distances. The average distance for biomass transportation to a large-scale conversion plant suitable for electricity or methanol production will be 30–42 km when the conversion plant is located in the centre of the biomass production area. The total energy efficiency of biomass production and transportation will be 95–97% and the emissions of air pollutants will be small. In areas where energy crops from agriculture constitute the main part of the biomass, the transportation distance will be two to three times shorter than in areas where logging residues from forestry dominate. When present Swedish fossil-fuel use for heat and electricity production is replaced, more than 75% of the biomass required can be produced locally within the county. The average transportation distance of the remaining part will be between 130 and 240 km, increasing the cost of this biomass by 15–20%. Increased use of biomass by 430 PJ/yr, the estimated potential for increased utilization of energy crops, logging residues and straw, will lead to an excess of about 200 PJ/yr biomass after fossil fuels for electricity and heat production have been replaced. This biomass could be used for methanol or electricity production. The production of biomass-based methanol will lead to a low demand for transportation, as the methanol produced from local biomass can mainly be used locally to replace petrol and diesel. If the biomass is used for electricity production, however, the need for transportation will increase if the electricity is cogenerated in district heating systems, as such systems are usually located in densely populated areas with a deficit of biomass. About 60% of the biomass used for cogenerated electricity must be transported, on average, 230 km. Changing transportation mode when transporting biomass over large distances, compared with short distances, however, will lead to rather low specific transportation costs and environmental impact, as well as high energy efficiency. Replacing fossil fuels with biomass for heat and electricity production is typically less costly and leads to a greater reduction in CO2 emission than substituting biomass for petrol and diesel used in vehicles. Also, cogeneration of electricity and heat is less costly and more energy efficient than separate electricity and heat production.

Future production and utilisation of biomass in Sweden: potentials and CO2 mitigation

Swedish biomass production potential could be increased significantly if new production methods, such as optimised fertilisation, were to be used. Optimised fertilisation on 25% of Swedish forest land and the use of stem wood could almost double the biomass potential from forestry compared with no fertilisation, as both logging residues and large quantities of excess stem wood not needed for industrial purposes could be used for energy purposes. Together with energy crops and straw from agriculture, the total Swedish biomass potential would be about 230 TWh/yr or half the current Swedish energy supply if the demand for stem wood for building and industrial purposes were the same as today. The new production methods are assumed not to cause any significant negative impact on the local environment. The cost of utilising stem wood produced with optimised fertilisation for energy purposes has not been analysed and needs further investigation. Besides replacing fossil fuels and, thus, reducing current Swedish CO2 emissions by about 65%, this amount of biomass is enough to produce electricity equivalent to 20% of current power production. Biomass-based electricity is produced preferably through co-generation using district heating systems in densely populated regions, and pulp industries in forest regions. Alcohols for transportation and stand-alone power production are preferably produced in less densely populated regions with excess biomass. A high intensity in biomass production would reduce biomass transportation demands. There are uncertainties regarding the future demand for stem wood for building and industrial purposes, the amount of arable land available for energy crop production and future yields. These factors will influence Swedish biomass potential and earlier estimates of the potential vary from 15 to 125 TWh/yr.

Wax esters produced by solvent-free energy-efficient enzymatic synthesis and their applicability as wood coatings

The study aimed at developing a process for making a wood coating wax based on the principles of green chemistry. The research was conducted within the Swedish interdisciplinary research programme Greenchem. Wax esters are attractive since they are non-hazardous, biodegradable and can be produced in an atom-efficient process from building blocks obtained from renewable resources. Four wax esters were prepared in a solvent-free process using an immobilised lipase as catalyst. When the water was removed during the process from what was initially an equimolar mixture of the starting materials carboxylic acid and alcohol by a stream of dry air passed through the reactor, there was a 95–99% conversion to the ester. The enzymatic process consumed 34% less energy and generated less waste than chemical esterification using a strong acid as catalyst. Two of the esters worked well in the industrial wood coating equipment employed and produced surfaces resistant to water and somewhat less to fat stains.

Seeing the wood for the trees: 25 years of renewable energy policy in Sweden

Sweden has a long-standing political commitment to the development of renewable energy, although the driving forces have changed over time. The focus has shifted from reducing dependence on oil to phasing out nuclear power, and, in the past 10 years, to reducing greenhouse gas emissions. In this article we review Swedish renewable energy policy since 1975, focusing on how it has influenced the development of wind power and the use of biomass for heat and electricity production. Sweden is endowed with rich renewable energy sources. The wind and bioenergy potential alone, about 100-200 TWh and 700 PJ, respectively, each correspond to more than one-third of present primary energy use. In 2001, about 500 GWh of wind power was produced and 336 PJ of biomass for energy was used. Renewable energy policy during the 1970s and 1980s was mainly expressed as strong efforts in technology research, development and demonstration. This supply-led attempt to transform the energy system had little impact on the Swedish energy balance. Market development took off mainly during the 1990s when taxes and subsidies created favourable economic conditions for new investments and fuel-switching. This underlines the importance of creating demand-pull policies. In the case of wind, Sweden still has only about one-fifth as much installed capacity as Denmark. The relatively slow development of wind power can be ascribed to the lack of strong commitment, continuity, and a clear strategy and approach in Swedish government efforts for the establishment and expansion of wind power – a situation that has been exacerbated by relatively low electricity prices. In contrast, the use of biomass for energy increased substantially during the 1990s, specifically wood fuels for district-heating which increased from 13 PJ in 1990 to 65 PJ in 2001. A system with high carbon dioxide taxes, 28 euro/t CO 2 in 1991 and 84 euro/t CO 2 in 2003, for fuels for heating but no taxes on fuels for electricity production created strong incentives for fuel-switching in district-heating, albeit not for biomass-based cogeneration. The development was facilitated by existing infrastructures in the forestry and energy sectors, notably the district-heating systems. Professional actors in these sectors were able to respond constructively to changes in relative fuel prices. A quota-based renewable electricity certificates system was introduced in 2003 to replace earlier subsidy schemes. In the next few years it is expected to stimulate mainly the development of biomass-based cogeneration.

Environmental effects of energy crop cultivation in Sweden-II: Economic valuation

In this paper, environmental benefits of the cultivation of perennial energy crops in Sweden, which have been identified and quantified in an earlier paper, are evaluated economically. Several different benefits, ranging from global to site-specific, could be achieved by replacing annual food crops with perennial energy crops. The economic value of these environmental benefits, including reductions in costs to farmers (direct costs) and to society as a whole (external costs), has been estimated to be from US

Life cycle assessment in green chemistry: overview of key parameters and methodological concerns

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