| 1. |
- Aguilar Cabezas, Francisco X
(författare)
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Assessment of residential wood energy consumption using German household-level data
- 2019
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Ingår i: Biomass and Bioenergy. - : Elsevier BV. - 0961-9534 .- 1873-2909. ; 126, s. 117-129
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Tidskriftsartikel (refereegranskat)abstract
- The residential sector accounts for about half of annual wood energy consumption in Germany. We applied a left-censored Tobit model to a cross-sectional dataset to quantify factors affecting household-level German residential wood energy consumption in years 2005, 2010 and 2014. Explanatory variables distinguished between (1) heating technology, dwelling characteristics and alternative energies; (2) woody biomass accessibility and weather; as well as (3) households' socio demographic characteristics. Results show that wood energy consuming households with central heaters used an additional 0.83-1.82 m(3) year(-1) of wood. Households' wood energy consumption showed a positive correlation with residence area and elastic responses to year of building construction. Greater elasticities in wood energy consumption were found when alternative energy prices exceeded US$ 1,050-1,330 per ton of oil-equivalent net calorific value. Local accessibility of woody biomass measured through forest ownership and forest density was associated with greater wood for energy consumption by an average 0.27-0.52 m(3) year(-1) and 0.13-0.25 m(3) year(-1), respectively. In addition, wood energy consumption increased proportionally with increasing rurality. Elasticity of household wood energy consumption with respect to heating degree days was estimated at 0.83-1.15. Among demographic variables, households at lower and higher income levels exhibited greater amounts of wood energy consumption. Results provide evidence that greater adoption of central wood energy heaters, price competitiveness of wood energy over alternative energies, and improving access to wood energy sources can lead to greater residential wood energy consumption in Germany.
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| 2. |
- Aguilar Cabezas, Francisco X
(författare)
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Comparison of small area estimation methods applied to biopower feedstock supply in the Northern US region
- 2019
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Ingår i: Biomass and Bioenergy. - : Elsevier BV. - 0961-9534 .- 1873-2909. ; 121, s. 64-77
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Tidskriftsartikel (refereegranskat)abstract
- Increasing interest in utilization of forest biomass for bioenergy has prompted extensive contemporary research regarding costs, supply and technology for efficiently producing electricity and other forms of renewable energy. One challenge facing both researchers and users is obtaining precise estimates of available forest biomass within plausible supply areas for individual power plants. Due to the wide distribution of power plants poised to co-fire with forest biomass, assessing its availability requires methods that can yield precise and low-bias estimates of aboveground forest biomass and other key attributes at varying spatial scales. Small area estimation (SAE) methods have high potential to accomplish this due to the availability of national forest inventory data, combined with satellite imagery and other forms of remotely-sensed auxiliary information. The study assessed several indirect, direct and composite estimators of four forest attributes: aboveground tree biomass, biomass of small-diameter trees, biomass of tops and limbs, and volume at the county-level and within the estimated supply areas around power plants across 20 states in the contiguous Northern U.S. Composite estimators using both k-nearest neighbors imputation and multiple linear regression provided superior estimates of indicators of forest biomass availability based on both precision and bias at the county-level at sampling intensities as low as 10-20%, compared to the other SAE methods examined. The composite estimator using k-nearest neighbors imputation was subsequently shown to produce precise estimates of forest biomass availability for selected power plant supply areas.
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| 3. |
- Ahlberg-Eliasson, Karin, et al.
(författare)
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Production efficiency of Swedish farm-scale biogas plants
- 2017
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Ingår i: Biomass and Bioenergy. - : Elsevier BV. - 0961-9534 .- 1873-2909. ; 97, s. 27-37
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Tidskriftsartikel (refereegranskat)abstract
- Biogas from agricultural waste streams represents an important way to produce fossil-free energy, allow nutrient recycling and reduce greenhouse gas emissions. However, biogas production from agricultural substrates is currently far from reaching its full potential. In Sweden, the number of biogas plants and their output have increased in recent years, but they are still experiencing harsh economic conditions. A recent evaluation (2010–2015) of 31 farm-scale biogas production facilities in Sweden sought to identify parameters of importance for further positive development. In this paper, data on plant operation, gas yield and digestate quality for 27 of these plants are summarised and statistically analysed to investigate factors that could allow an increase in overall biogas production and in nutrient content in the digestate. The analysis showed that addition of co-substrates to manure results in higher gas production, expressed as both specific methane potential and volumetric gas production, than when manure is the sole substrate. Use of co-substrate was also found to be influential for the nutrient content of the digestate. These observed improvements caused by co-digestion should be considered when subsidy systems for manure-based biogas processes are being created, as they could also improve the economics of biogas production. However, to achieve higher efficiency in existing biogas plants and to improve the situation for future investments, a more detailed, long-term evaluation programme should also be considered.
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| 4. |
- Ahmed, Ali, 1977-, et al.
(författare)
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Biomass energy, technological progress and the environmental Kuznets curve: Evidence from selected European countries
- 2016
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Ingår i: Biomass and Bioenergy. - : Pergamon Press. - 0961-9534 .- 1873-2909. ; 90, s. 202-208
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Tidskriftsartikel (refereegranskat)abstract
- We examine the causal relationship between economic growth and CO2 emissions in a panel of 24 European countries from 1980 to 2010. Using an analytical framework that considers pooled mean group estimations in a dynamic heterogeneous panel setting, we show that there is an inverted U-shaped relationship between CO2 emissions and economic growth in the long run and that there is no such relationship in the short run. In particular, we find that biomass energy is insignificantly linked to CO2 emission. However, technological innovation significantly facilitates reduction of CO2 emissions in the investigated countries. Altogether, our study implies that economic growth and environmental quality can be achieved simultaneously, which opens up new insights for policy-makers for sustainable economic development via implementation of renewable energy consumption through technological innovation.
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| 5. |
- Alamia, Alberto, 1984, et al.
(författare)
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Design of an integrated dryer and conveyor belt for woody biofuels
- 2015
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Ingår i: Biomass and Bioenergy. - : Elsevier BV. - 1873-2909 .- 0961-9534. ; 77, s. 92-109
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Tidskriftsartikel (refereegranskat)abstract
- Combustion or gasification of high-moisture content biomass is associated with a number of drawbacks, such as operational instabilities and lowered total efficiency. The present work proposes an integrated dryer and conveyor belt for woody biofuels with steam as the heat transfer medium. The use of low-temperature steam is favorable from a heat management point of view, but also helps to minimize the risk of fire, self-ignition and dust explosions. Furthermore, the presented dryer design represents an efficient combination of fuel transport, drying equipment and fuel feeding system.The proposed design is developed from a macroscopic energy and mass balance model that uses results from computational fluid dynamics (CFD) fuel bed modeling and experiments as its input. This CFD simulation setup can be further used to optimize the design with respect to bed height, steam injection temperatures and fuel type. The macroscopic model can be used to investigate the integration of the dryer within a larger biomass plant. Such a case study is also presented, where the dryer is tailored for integration within an indirect steam gasification system. It is found that the exergy efficiency of this dryer is 52.9%, which is considerably higher than those of other dryers using air or steam, making the proposed drying technology a very competitive choice for operation with indirect steam gasification units.
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| 6. |
- Albertsson, Johannes, et al.
(författare)
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Effects of mechanical weed control or cover crop on the growth and economic viability of two short-rotation willow cultivars
- 2016
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Ingår i: Biomass and Bioenergy. - : Elsevier BV. - 0961-9534 .- 1873-2909. ; 91, s. 296-305
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Tidskriftsartikel (refereegranskat)abstract
- Willow grown as short rotation coppice (SRC) is sensitive to weed competition, so herbicide treatment combined with mechanical weed control is recommended when establishing a plantation. This study compares that practice with two mechanical, row crop cultivator (RC) and row crop cultivator with torsion weeder (RCT), and two cultural treatments, cover crop (CC) and cut cover crop (CCC), to control weeds. Willow responses to these treatments were compared during the first three years after planting using two cultivars, Gudrun and Tordis with broad and narrow leaves, respectively. At harvest, the RCT treatment had produced 27% more biomass than the RC treatment (13.9 vs 11.0 Mg ha(-1) dry matter) and approximately three times more than the cultural treatments. However, the standard control treatment, herbicides and row crop cultivator (HRC), produced more than all other treatments (17.3 Mg ha(-1) dry matter). The two cultural treatments had higher plant mortality (CC 26.2% and CCC 32.8%) than the other treatments (HRC 2.7%, RC 7.0% and RCT 7.0%) after the first harvest cycle. No interaction between cultivar and treatment was found for willow shoot biomass, weed biomass or plant mortality. Overall, however, Gudrun had lower plant mortality and less weed biomass after the first harvest cycle than Tordis. All treatment and cultivar combinations gave positive financial annual returns when the whole life-span of the plantation was considered. This study suggests that without using herbicides, it is possible to establish a willow SRC plantation that produce enough to be economically viable. (C) 2016 Elsevier Ltd. All rights reserved.
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| 7. |
- Anasontzis, George E, 1980, et al.
(författare)
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Rice straw hydrolysis using secretomes from novel fungal isolates from Vietnam
- 2017
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Ingår i: Biomass and Bioenergy. - : Elsevier BV. - 1873-2909 .- 0961-9534. ; 99, s. 11-20
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Tidskriftsartikel (refereegranskat)abstract
- With a production of 39 million metric tons each year, rice is one of the main agricultural products of Vietnam. Thus, rice straw is a significant by-product, whose use in a biorefinery process would contribute to the bio-based transformation of the Vietnamese and South East Asian economy. In order to find novel efficient enzyme mixtures for the hydrolysis of rice straw and other agricultural residues, we took advantage of the rapidly evolving biodiversity of Vietnam and screened 1100 new fungal isolates from soil and decaying plant tissues for their CMCase activity. We selected 36 strains and evaluated them for their cellulases, xylanases, and accessory enzymes activities. Most of these isolates belonged to the genera Aspergillus and Trichoderma. We identified a few promising isolates, such as A. brunneoviolaceus FEC 156, A. niger FEC 130 and FEC 705, and A. tubingensis FEC 98, FEC 110 and FEC 644, whose produced enzyme mixtures released a mass fraction of the sugar content of alkali-treated rice straw higher than 20%, compared to 10% for Trichoderma reesei RUT C-30. We verified that the black Aspergilli are particularly efficient in their saccharification ability. We also identified strains that although they produced low amounts of cellulases and xylanases, their enzyme mixtures had high saccharification efficiencies, indicating the importance of the synergy effect, rather than the amount of enzymes available. Our results highlight the intra-species variation, especially in the Trichoderma genus, regarding the biomass degradation characteristics and the associated range of enzymatic activities.
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| 8. |
- Arrhenius, Karine, et al.
(författare)
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Suitability of vessels and adsorbents for the short-term storage of biogas/biomethane for the determination of impurities – Siloxanes, sulfur compounds, halogenated hydrocarbons, BTEX
- 2017
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Ingår i: Biomass and Bioenergy. - : Elsevier BV. - 0961-9534 .- 1873-2909. ; 105, s. 127-135
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Tidskriftsartikel (refereegranskat)abstract
- Biogas is a renewable energy source with many different production pathways and various excellent opportunities to use, for example as vehicle fuel (biomethane). Reliable analytical methodologies for assessing the quality of the gas are critical to ensure that the gas can technically and safely be used. An essential part of any procedure aiming to determine the quality is the sampling and the transfer to the laboratory. One of the greatest challenges is then to ensure that the composition of the sample collected does not change between the time of sampling and the analysis. The choice of the sampling vessel to be used must be made only after fully assessing its short-term stability. In this paper, the results from short-term stability studies in different vessels (cylinders, bags and sorbents) are presented for siloxanes, BTEX, halogenated hydrocarbons and sulfur compounds. Storage of dry gas at high pressure (> 6 MPa) appears to be a good alternative however it is currently challenging to find an optimal treatment of the cylinders for all species to be assessed in biogas/biomethane. At lower pressure, adsorption effects on the inner surface of the cylinders have been observed. The use of bags and sorbent tubes also shows limitation. No existing sorbent tubes are sufficiently universal as to trap all possible impurities and high boiling compounds may adsorbed on the inner surface of the bags walls. Moreover, the presence of water when storing biogas most certainly impacts the storage stability of compounds in most vessels. Using at least two sampling methods for a given compound and comparing results will allow taking into account the eventual effects of water vapour, and adsorption on the inner surface of the vessels.
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| 9. |
- Bach-Oller, Albert, et al.
(författare)
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Fuel conversion characteristics of black liquor and pyrolysis oil mixtures: Efficient gasification with inherent catalyst
- 2015
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Ingår i: Biomass and Bioenergy. - : Elsevier BV. - 0961-9534 .- 1873-2909. ; 79, s. 155-165
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Tidskriftsartikel (refereegranskat)abstract
- Alkali metals inherent in black liquor (BL) have strong catalytic activity during gasification. A catalytic co-gasification process based on BL with pyrolysis oil (PO) has the potential to be a part of efficient and fuel-flexible biofuel production systems. The objective of the paper is to investigate how adding PO into BL alters fuel conversion under gasification conditions. First, the conversion times of single fuel droplet were observed in a flat flame burner under different conditions. Fuel conversion times of PO/BL mixtures were significantly lower than PO and comparable to BL. Initial droplet size (300–1500 μm) was the main variable affecting devolatilization, indicating control by external heat transfer. Char oxidation was affected by droplet size and the surrounding gas composition. Then, the intrinsic reactivity of char gasification was measured in an isothermal thermogravimetric analyser at T = 993–1133 K under the flow of CO2–N2 mixtures. All the BL-based samples (100% BL, 20% PO/80% BL, and 30% PO/70% BL on mass basis) showed very high char conversion. Conversion rate of char gasification for PO/BL mixtures was comparable to that of pure BL although the fraction of alkali metal in char decreased because of mixing. The reactivities of BL and BL/PO chars were higher than the literature values for solid biomass and coal chars by several orders of magnitude. The combined results suggest that fuel mixtures containing up to 30% of PO on mass basis may be feasible in existing BL gasification technology.
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| 10. |
- Bergström, Dan
(författare)
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Productivity of harvesting dense birch stands for bioenergy
- 2016
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Ingår i: Biomass and Bioenergy. - : Elsevier BV. - 0961-9534 .- 1873-2909. ; 88, s. 142-151
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Tidskriftsartikel (refereegranskat)abstract
- Marginal lands could be utilized for increasing energy biomass production independent of industrial roundwood procurement. Dedicated energy biomass production systems on such sites would be based on low stand establishment cost, clear-cutting at an early stage, and coppice regeneration. Harvesters designed for the processing of industrial roundwood are inefficient or too costly to use in small-diameter and dense stands, while insufficient cutting capacity and uneven space distribution of trees limit the use of modified agricultural harvesters developed for short-rotation woody-crop plantations (e.g. willow). We constructed time consumption models for clear-cutting and forwarding of whole trees from unthinned, small-diameter stands. The data originated from naturally afforested downy birch-dominated stands located in a cutaway peat production area in northern Finland. Stand age varied from 14 to 29 years and stand density was 5150-160,250 trees per hectare. In clear-cutting, a medium-sized forest harvester equipped with an accumulating felling head fitted with a circular saw disc was used, and subsequent forwarding was done using a modified medium-sized forwarder. Cutting productivity was 3-11oven-dry tons (ODt) per effective hour (E-0-h), and was highly dependent on stand characteristics (e.g. mean whole-tree volume). At a distance of 300 m, for example, the productivity of forwarding in the time study plots was 6.7-10.4 ODt E-0-h(-1). Our study indicates that energy biomass can be harvested from young downy birch thickets efficiently by clear-cutting with appropriate machinery. (C) 2016 Published by Elsevier Ltd.
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