Environmental assessment of wood and non-wood based products

Resumo

Life Cycle Assessment (LCA) has proved to be an useful tool for the environmental evaluation of a product from a holistic point of view. With this perspective, a possible prejudiced analysis is avoided as it in fact deals with the diverse range of environmental impacts that flow from the industrial activities required for the manufacture of the industrial products under study in this dissertation. In this thesis, the application of LCA methodology was focused on the manufacture of cellulose and lignin based products derived from wood and non-wood raw materials. The forest based industry in Europe is of economic and social importance because of its production value, the incomes from exports and the employment in this sector. For this reason, several case studies were proposed and studied from a cradle-to-gate perspective. On the one hand, Spain and Sweden were chosen as representative countries of eucalypt (hardwood) and, pine and spruce (softwood) producer countries, respectively and forest operations focused on pulpwood production were assessed from field management to roundwood delivery to pulp mills located in Spain and Sweden. On the other hand, three representative forest products, which play an important role in forest sector, were studied: eucalypt kraft TCF pulp, softwood dissolving TCF pulp and softwood hardboards. One objective of this thesis was to analyse the environmental pressure of all of them and to identify options to reduce these pressures. Moreover, the thesis was centred on other alternative raw materials to forest industry due to the pressure exerted by different world organizations because of changes in agricultural policies, wood supply issues and environmental aspects. In this context, several case studies were also proposed. Firstly, agricultural activities related to hemp and flax cultivation were identified and assessed. Both crops were chosen due to they are traditional non-wood fibre crops in Spain and other European countries. Secondly, fibres obtained from both crops are commonly used as raw material in specialty paper pulp mills so, this industrial stage was also taken into account in order to quantify the environmental burdens associated. Thirdly, wood parts separated from hemp and flax straw have composition similar to wood species with a high content of cellulose and hemicellulose. The potential of second generation bioethanol production was also analysed since the present energy system is clearly unsustainable: fossil fuel resources are limited and, particularly in the case of mineral oil, are rapidly being depleted. Bioenergy and specifically, bioethanol, is now a key option in many countries'energy policies. Therefore, throughout this thesis, specific attention was given to identify knowledge gaps, and possibilities and limitations of strategies to increase the sustainability of all these production systems. The work carried out has proved that LCA methodology is well suited to fulfil the objectives proposed: the acquisition of environmental data, the generation of information on the relative importance of the environmental impact of the different life cycle steps as well as the development of a scientific basis for the proposal of improvement actions that outcome in a better environmental performance of the systems under study.