Life cycle impact assessment of alternative boat building material in Bangladesh

Abstract

Country boats with a population estimated in excess of 1 million makes an immense contribution to national economy and provides employment for 4 million people. Traditionally, these boats are made of timber. Spiraling price and deteriorating quality has resulted in a need to look for alternative material for building such boats. Several options may be considered such as aluminium, steel, ferrocement, fiberglass plastic. The present work aims to make a comparative evaluation of environmental friendliness of the different options available for building country boats. The Life Cycle Assessment (LCA) methodology has been adopted for the analysis and comparison of the different options. In order to carry out the analysis, extensive data collection were undertaken to estimate the number of boats, amount of timber presently being consumed for building and repairing boats. The timbers were segregated into forest timber and backyard timber. All data on timber consumption were converted to round log equivalent. Other materials required for building and repair were also estimated. The change in the number of boats resulting from change in building material and consequent hull shape modification has been estimated. The materials required for these boats were estimated from preliminary designs. Operating lives of the boats were assumed 20 years and accordingly the materials required for operation and maintenance of the boats were also estimated. The LCA analysis requires that environmental loads that were generated when these materials were produced be taken into account. There loads are evaluated in terms of emission of heat, carbon dioxide, methane, tetra chloromethane, nitrogen oxides, sulfur oxides, CFCs etc. Such data for mass produced industrial items such as steel, aluminium and commonly used chemicals derived from industrial data and are readily available, but not for timber, the main issue of the current study. In order to estimate this impact, an exhaustive literature survey was conducted to explore how this is done in LCA procedures. Some literatures on LCA of pulp and paper production, building materials etc. were studied which shows that researchers have dealt elaborately into the different complexities in such a procedure. However, there appears to be no accepted methodology. for taking timber consumption into account in LCA. Although some schematic models have been suggested no results have been presented by any researcher The current work has developed a methodology for the estimating (in LCA format) the environmental impact of felling a tree. In doing so, the renewability aspect of the tree has been taken into especial consideration. The virtual emission of CO2 is taken to be the amount of CO2 that the tree would have absorbed had the tree not been felled. However, this is reversed by the new trees planted after felling one which is the present practice as far as backyard forestry or managed forestry is concerned. It requires some time before the newly planted trees start compensating the loss from cutting a tree and, under some conditions, may even contribute more. This scenario will depend upon a number of parameters such as the species of the felled tree, number and species of the new saplings planted, bio-mass accumulation rate of the saplings planted, forest density and subsequent mortality rate etc. The model developed was then applied to the scenario of timber resources in the country to estimate the future virtual CO2 emission. Unlike emission caused by industrial processes data, the CO2 emission scenario for tree felling has a time element and thus further treatment of the data were required before the same may be fed into LCA format. This has been achieved by utilizing guidelines provided by some researchers. Topsoil erosion is one of the major impacts of deforestation. Because of non-availability of data and absence of any correlation of this phenomenon with LCA format, this impact was not included in the study. The data on virtual CO2 emission thus arrived at was used for a comparative LCA of the different materials available for building country boats. The impact categories considered are global warming, ozone layer depletion, ecotoxocological impacts and eutrophication. The results presented show that for a 20 year time horizon timber is the most harmful to the environment in terms of global waiming potential and ferrocement is the least. For a 100 years time horizon, timber is better than steel and aluminium. For ozone depletion potential of FRP is worst in both 20 years and 100 years time horizon. Timber and ferrocement are the best choices in preserving ozone layer. Again timber is the best in ecotoxicological impacts and FRP performing worst in both 20 and 100 years time horizon. As far as eutrophication is concerned timber is again the best and the FRP worst. The poor performance of the FRP is because of the large volume of toxic and harmful chemical that need to be produced for building FRP boats. The thesis concludes with emphasizing a need to develop/refine tools for estimation of the environmental impacts of deforestation. It is also highlighted that this model, with necessary improvements may be utilized in LCA procedures for pulp and paper industry, furniture, building etc. A broad work incorporating different disciplines to carry out a comprehensive was recommended.