Life cycle assessment of a parabolic solar cooker and comparison with conventional cooking appliances

Abstract

Cooking is a basic human need and is realised worldwide using several kinds of appliances, many of them requiring the direct or indirect use of fossil fuels to operate. It thus creates large amount of greenhouse gas emissions in addition to other damages to the environment and human health. Life Cycle Assessment (LCA) helps at quantifying the potential environmental impacts and at identifying the sustainable cooking practices. Here, LCA was used to evaluate the environmental performances of three western conventional cooking appliances (induction hob, electric plate and gas hob) and to compare them with those of a parabolic solar cooker declined with several materials (10 models in total). The functional unit was defined as to heat 2 L of water from room temperature to boiling temperature, three times a day, every day during 40 years. Experiments were performed to quantify the Energy consumption and the devices' composition. LCA was performed with Umberto LCA+ software with ecoinvent database, and ReCiPe method was used to for the impacts assessment with both end-point and mid-point approaches. The worst solar cooker (made on Chinese aluminium) has a cradle-to-grave climate change impact of 264 kgCO2eq while the solar device made in wood and recycled aluminium performs the best with 58 kgCO2eq. Concerning the conventional devices, the less impacting is the induction hub (847 kgCO2eq) followed by the electric plate (1085 kgCO2eq) and gas hob with the worst impact (3736 kgCO2eq), on a cradle-to-grave base. The construction stage contributes with 463, 266 and 85 kgCO2eq for the gas hob, the electric plate and the induction hob respectively. These results demonstrate that the energy consumption in the use stage is the most contributors to climate change impact. The absence of energy consumption with the solar cookers also prevent from other impacts like particulate and oxidant formation and damages on human health. Globally, the device with the highest cradle-to-grave impacts on most of the mid-point indicators (11 out of 18) is the electric plate. In comparison, the solar cookers always have lower impacts than the conventional ones except for the agricultural land occupation where the wood and Chinese aluminium parabola dominates. The impact of the latter is 161 m2·yr mainly due to the use of wood (156 m2·yr) against 95 m2·an which is the highest for the conventional cookers (electric plate). In terms of end points, the overall aggregated cradle-to-grave damage of the worst solar cooker is 25 points (Chinese aluminium), while for the cleaner conventional device is 112 points (induction hob). Among the 10 models of solar cookers, those made on wood and recycled aluminium strongly reduce the impacts compared to those fully made on aluminium. Additionally, a sensitivity analysis was performed by varying the lifespan of the cookers, the grid's carbon intensity, the annual energy consumption for cooking and the lifespan of the structure of the aluminium solar cooker. Finally, the conditions for an ecological benefit of solar cooking were analysed as well as the economic accessibility. Overall, in almost all scenarios, the solar cooker is ecologically beneficial, although its environmental performance depends on the composing materials and the frequency of use. These results demonstrate that solar cooking can be considered as a credible sustainable cooking practice.