Goal, Scope and Background
Agricultural production includes not only crop production, but also food processing, transport, distribution, preparation, and disposal. The effects of all these must be considered and controlled if the food chain is to be made sustainable. The goal of this case study was to identify and review the significant areas of potential environmental impacts across the whole life cycle of cane sugar on the island of Mauritius.
Methods
The functional unit was one tonne of exported raw sugar from the island. The life cycle investigated includes the stage of cane cultivation and harvest, cane burning, transport, fertilizer and herbicide manufacture, cane sugar manufacture and electricity generation from bagasse. Data was gathered from companies, factories, sugar statistics, databases and literature. Energy depletion, climate change, acidification, oxidant formation, nutrification, aquatic ecotoxicity and human toxicity were assessed.
Results and Discussion
The inventory of the current sugar production system revealed that the production of one tonne of sugar requires, on average, a land area of 0.12 ha, the application of 0.84 kg of herbicides and 16.5 kg of N-fertilizer, use of 553 tons of water and 170 tonne-km of transport services. The total energy consumption is about 14235 MJ per tonne of sugar, of which fossil fuel consumption accounts for 1995 MJ and the rest is from renewable bagasse. 160 kg of CO2 per tonne of sugar is released from fossil fuel energy use and the net avoided emissions of CO2 on the island due to the use of bagasse as an energy source is 932,000 tonnes. 1.7 kg TSP, 1.21 kg SO2,1.26 kgNOxand 1.26 kg CO are emitted to the air per tonne of sugar produced. 1.7 kg N, 0.002 kg herbicide, 19.1 kg COD, 13.1 kgTSS and 0.37 kg PO43- are emitted to water per tonne of sugar produced. Cane cultivation and harvest accounts for the largest environmental impact (44%) followed by fertilizer and herbicide manufacture (22%), sugar processing and electricity generation (20%), transportation (13%) and cane burning (1%). Nutrification is the main impact followed by acidification and energy depletion.
Conclusions
There are a number of options for improvement of the environmental performance of the cane-sugar production chain. Cane cultivation, and fertilizer and herbicide manufacture, were hotspots for most of the impact categories investigated. Better irrigation systems, precision farming, optimal use of herbicides, centralisation of sugar factories, implementation of co-generation projects and pollution control during manufacturing and bagasse burning are measures that would considerably decrease resource use and environmental impacts.
Recommendation and Outlook
LCA was shown to be a valuable tool to assess the environmental impacts throughout the food production chain and to evaluate government policies on agricultural production systems.