Biomass最新文献

Biomass energy and human labour are the two main driving forces for functioning of the agriculture-based village ecosystem of Bhabinarayanpur. In the ecosystem, 97·6% of the total fuel energy consumption during the year was derived directly or indirectly from biomass. The direct biomass fuel consumption was 9636 GJ during the year (84%). The other forms of energy used were human labour (1012 GJ year⁻¹; 9%) and draught animal (580 GJ year⁻¹; 5%) for agriculture and domestic purposes. Production and consumption patterns of energy with its outflow and inflow showed that the village was an open and self-insufficient ecosystem. In the present study, an energy-flow model for the village ecosystem was also prepared.

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

The project ‘Harvesting Early Thinnings for Energy’ involved eight participating countries: Canada, Denmark, Finland, New Zealand, Norway, Sweden, the UK and the US. The aim of the project was to investigate possibilities and initiate activities within and between the participating countries to advance the development of harvesting systems in early thinnings. Eight sub-projects were completed: (1) felling methods and technology, (2) bunch delimbing, (3) integrated harvesting, (4) microtractors for harvesting energy wood, (5) thinning with small crawler tractors, (6) small-scale harvesting of hardwood thinnings for energy, (7) forest transport of energy wood on soft terrain, and (8) chipping methods and technology. The results of these studies are reported.

A generalized procedure for quantifying the benefits of household biogas plants is presented. The sensitivity of the procedure to the uncertainty in input prices is reduced through the assumption of incremental benefits from the biogas plant. These benefits are quantified in terms of the quantity of fuelwood for which the biogas substitutes in cooking, the quantity of kerosene replaced through the use of biogas for lighting and the diesel fuel displaced through the use of a biogas fuelled dual-fuel engine for motive power.

Sensitivity of the monetary benefits for these parameters is examined in order to identify variable which influence the viability of the technology to the end user.

The feasibility of producing biogas by anaerobic digestion of a nitrophilic algae biomass obtained from the highly eutrophicated Venice Lagoon has been investigated. Methods for harvesting algal biomass have been examined in detail and different pretreatments used prior to analysis and digestion of the algae described. Results obtained from three pilot plant digesters over a period of 12 months using Ulva rigida and Gracilaria as feed material gave no indication of inhibition of the process by either high salinity or high metals content resulting from pollutants discharged into the lagoon. Sulphides were formed during digestion as a consequence of the high sulphate content of the interstitial water as well as the level of sulphur present in the algae. However, the sulphides did not appear to cause inhibition or result in a reduction in gas yield. A maximum biogas production rate of 0·347 m³ kg VS⁻¹ day⁻¹ was obtained during digestion at a retention time of 20 days with an organic loading rate of 1 kg VS m⁻³ day⁻¹.

Economic evaluations were added, for the first time, as a formal ‘Activity’ in the 1986 International Energy Agency Bioenergy Agreement task II. The objective of the ‘Activity’ was to economically evaluate the state of the art for short-rotation biomass production systems. This was done through three significant economic workshops, a comprehensive annotated bibliography, the development and testing of a standardized cost accounting spreadsheet for reporting cost informations, and the publishing of numerous technical papers. Given the economic climate during 1986–88, short-rotation woody crop systems for energy appeared marginal in most instances without government incentives.

Short rotation intensive culture (SRIC) plantations, established in central Pennsylvania, were analyzed to determine their economic optimum rotation age. The general management design for the plantations used fertilized and non-fertilized strategies, a tree spacing of 0·48 m² and a rotation length of 4 years. A stand-level financial model analyzed the unit cost of production for alternate rotation lengths based upon the plantation's investment and operating costs and resulting biomass yields.

Analysis of the first two rotations indicated that the minimum unit cost for fertilized and non-fertilized strategies was in the fourth year of the first rotation and the third year of the second rotation. Growth curves for the rotations also showed a maximum volume production at the same points in the rotations. Selection of a 3-year rather than 4-year harvest during the second rotation would reduce unit costs by 14% in the non-fertilized strategy and by 15% in the fertilized strategy.

Eleven district heating plants were visited in the autumn and winter 1987–1988 to interview the staff and Measurement Association to determine how the wood fuel was evaluated. The geographical distribution of the heating plants ranges from Vaxjo in the south to Ostersund in the north. The plants for solid fuel vary in size from 5 MW to 65 MW. Wood fuel consumption ranged from 70 000 to 450 000 m³/year. The average wood transport distance is about 50 km. The number of wood fuel assortments handled at delivery varies from one single assortment to as many as 75. Payment for wood fuel is mainly on the basis of MW h delivered, and therefore most plants have a mechanism for determining moisture content and a formula for calculating energy value.

A field experiment was conducted at the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) Center, Patancheru, India to study photosynthetically active radiation (PAR) interception and dry matter production relationships in pearl millet (Pennisetum americanum (L.) Leeke). Two pearl millet genotypes, BJ 104 (G₁) and ICH 226 (G₂) were sown at three planting geometries obtained by using combinations of row and plant spacings (S₁: 37·5 cm × 26·6 cm; S₂: 75·0 cm × 13·3 cm; S₃: 150·0 cm × 6·6 cm) such that plant population was constant at 100 000 ha⁻¹ in all treatments. Cumulative intercepted PAR was maximum (330 MJ m⁻²) in G₂S₂ and minimum (268 MJ m⁻²) in G₁S₃. Conversion efficiency values ranged from 1·87 g MJ⁻¹ in G₁S₂ to 2·32 g MJ⁻¹ in G₂S₃. Final above-ground dry matter followed the pattern of cumulative intercepted PAR and maximum dry matter (7·22 Mg ha⁻¹) was produced by G₂S₂ while G₁S₃ produced minimum dry matter (4·97 Mg ha⁻¹).