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Item Applications of linear modelling in energy analysis : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Technology at Massey University(Massey University, 1984) Patterson, Murray GrahamThe primary objective of this study was to explore the use of classical linear models in Energy Analysis; so as to resolve some of the methodological problems associated with Energy Analysis, and to extend the scope and potential of Energy Analysis as a scientific discipline. This was undertaken in the form of two separate yet related discourses. The first discourse provided a basis for resolving the energy quality problem encountered in Energy Analysis. A general equation was hypothesized and tested: [Equation] The matrix of simultaneous linear equations represented by this equation is usually overdetermined. Therefore, an appropriate solution method is a fitting procedure, such as regression. Further, in order to solve this general equation, one coefficient must arbitrarily be given a value equal to unity. Hence, all estimated coefficients are expressed in terms of multiples of that coefficient (termed quality equivalents). The general equation was first tes ted for the 1 97 6 New Zealand economy, so as to estimate 'actual' quality coefficients. Subsequently, the general equation was tested for a notional 'energy efficient' New Zealand economy, so as to estimate 'long run' quality coefficients, which reflected thermodynamic limits. Generally very accurate estimates of the coefficients were obtained. The solutions to the equations indicated that hydroelectricity was the highest quality primary energy source, followed by natural gas, oil, coal and then wood. The second discourse examined the 'optimal' use of primary energy resources in the New Zealand food system, using the formalism of Linear Programming. A preliminary discussion concluded that the concept of 'optimality' had greater potency than the concept of 'efficiency' in evaluating the use of energy resources, particularly in food systems. For each food sector (Production, Processing, Export-Import, Distribution, Catering and Household), coefficient matrices were assembled, drawing on literature data. Various combinations of constraints and objective functions were applied, in different Runs. The main objective functions used were minimising energy inputs for providing a nutritionally adequate diet , or maximising net energy gain from exporting agro-food products. The most critical constraints were found to be land area and market demand constraints. Detailed results of the Linear Programming runs are presented and discussed. An energetically 'optimal' diet was found to consist of large amounts of cereals, significant amounts of fresh fruit and vegetables and dairy products, and a very small amount of meat. Such a diet provided the Recommended Daily Allowances, for all nutritional elements, for the New Zealand population. Meat, Fish and Dairy products were found to have a particularly important function as commodities to be traded for imports of oil and energy intensive goods. A final discussion reviewed the use of Linear Models in Energy Analysis, and future directions for growth and development in Energy Analysis.Item An environmentally-based systems approach to sustainability analyses of organic fruit production systems in New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Sustainable Agricultural Systems at Massey University, Palmerston North, New Zealand(Massey University, 2009) Page, GirijaAn environmentally-based systems approach to sustainability analyses of organic fruit production systems in New Zealand. This research introduces an approach for the assessment of the sustainability of farming systems. It is based on the premises that sustainability has an environmental bottom line and that there is very limited substitutability between natural capital and other forms of capital. Sustainability assessment is undertaken through analyses of energy and material flows of the system and their impacts on the environment. The proposed sustainability assessment approach is based on two high level criteria for sustainability: efficient use of energy and non-degradation of the environment from energy and material use. Sustainability assessment of organic orchard systems in New Zealand was undertaken to demonstrate this approach. Five indicators which address the two criteria for the sustainability of the orchard systems are the energy ratio, the CO2 ratio, changes in the soil carbon level, nutrient balances, and the leaching of nitrogen. Organic kiwifruit and organic apple systems are modelled based on their key energy and material flows and their interactions with the natural environment. The energy and material flows are converted into appropriate energy and matter equivalents based on coefficients taken from the published literature. Sustainability indicators are estimated over one growing season using two computer modelling tools, Overseer® and Stella®, in a life cycle approach. Sustainability assessment of the organic orchard systems suggests that the approach is useful for evaluating energy use and key environmental impacts that occur in soil, water and atmosphere. The results indicate that the model organic orchard systems are sustainable in terms of energy use and are a net sink of CO2-equivalent emissions. The implication of this result is that organic orchard systems potentially could trade carbon credits under the Kyoto Protocol. The findings also suggest that the sustainability assessment approach is capable of identifying the trade-offs within the sustainability indicators associated with particular management practices. Further research to improve and validate the proposed approach is essential, before it can be practically used for decision making at the orchard level and for policy making at the national level.