Marginally Adjusted Average LCA - Bridging the Gulf Between Attributional and Consequential LCA
Issue:
Volume 6, Issue 2, June 2021
Pages:
17-26
Received:
2 May 2021
Accepted:
17 May 2021
Published:
27 May 2021
Abstract: Life Cycle Assessment (LCA) can often reveal unexpected or perverse outcomes from environmental initiatives. There are two main approaches to LCA: Attributional (ALCA) typically measures the impacts arising from producing a functional unit of product from average market suppliers and technologies. Consequential (CLCA) measures the marginal impacts to produce an additional functional unit of product, assuming that the resources consumed will come from new marginal supplies/technologies. As a result, ALCA and CLCA studies can give very different outcomes. The choice of method used for different LCA applications has divided practitioners and gives conflicting advice to decision-takers. The premise of this paper is that new production only causes marginal technologies to enter a market if the new producer specifically contracts the new marginal technology resources (e.g. Google sponsoring Solar Power for its operations). If the producer still purchases resources from average markets, then it is the aggregate demand in each market that motivates the entry of new marginal technologies and the effects of any addition should be shared with all co-consumers. The additional resources consumed are really the marginally adjusted average (MAA), not just the marginal. CLCA MAA results will usually closely resemble ALCA results, because entire markets are usually only perturbed to a small degree to meet new demand. In rare cases, where the existing market is substantially perturbed by an added demand, the CLCA results will differ significantly from the ALCA results. Many advantages are given for use of MAA to assess CLCA impacts, not least being to diminish the controversy between ALCA and CLCA outcomes.
Abstract: Life Cycle Assessment (LCA) can often reveal unexpected or perverse outcomes from environmental initiatives. There are two main approaches to LCA: Attributional (ALCA) typically measures the impacts arising from producing a functional unit of product from average market suppliers and technologies. Consequential (CLCA) measures the marginal impacts ...
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Evaluation of Impact Hammer Mill for Limestone Crushing for Acidic Soil
Issue:
Volume 6, Issue 2, June 2021
Pages:
27-32
Received:
14 May 2021
Accepted:
6 July 2021
Published:
13 July 2021
Abstract: Soil acidity becomes a serious threat to crop production in most highlands of Ethiopia particularly in Western parts of Oromia. Frequent tillage, removal of crop residues and mono-cropping and heavy rainfall contributes to soil acidification by leaching of cations. Agricultural limestone raises soil pH and reduces solubility of potentially toxic elements such as hydrogen, aluminum (Al3+) and manganese (Mn) at optimum nutrient uptake by crops. To elucidate problems associated with soil acidity, a motorized agricultural limestone crusher was fabricated and evaluated. Performance of the prototype hammer mill machine, in terms of crushing capacity (kg/h), crushing efficiency (%), mean particle size (mm), fuel consumption (ml/kg) or energy consumption (wh/kg) was evaluated. Tests were carried out at engine speeds of 540, 720, 900 rpm, screen hole diameter of 2, 4, 6 mm and feed rates of 3.50, 7.00, 10.50 kg/min. The highest crushing capacity 630.32 kg/hr was recorded at 900 rpm engine speed, 6mm screen hole diameter and at 10.50 kg/min feed rate whereas the minimum 65.62 kg/h was observed at 540 rpm hammer mill speed, 2 mm screen hole diameter and at 3.50 kg/min feed rate. The mean consumed energy ranged from 15.47 to 149.16 Wh/kg with hammer rotor speed of 540 to 900 rpm, screen hole diameter of 2 to 6 mm and the feeding rate of 3.5 to 10.5 kg/min. The mean particle size ranged from 0.121 to 0.448 mm with hammer rotor speed of 540 to 900 rpm, screen holes diameter of 2 to 6 mm and the feeding rate of 3.5 to 10.5 kg/min. It could be noticed that the lowest values of mean particle size were obtained at engine speed of 900 rpm, screen hole diameter of 2 mm and feed rate of 10.5 kg/min.
Abstract: Soil acidity becomes a serious threat to crop production in most highlands of Ethiopia particularly in Western parts of Oromia. Frequent tillage, removal of crop residues and mono-cropping and heavy rainfall contributes to soil acidification by leaching of cations. Agricultural limestone raises soil pH and reduces solubility of potentially toxic el...
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