Patrick Rousseaux

An LCA of alternative wastewater sludge treatment scenarios

Life Cycle Assessment (LCA) was carried out in order to compare the environmental impacts of five alternative treatment scenarios of sewage sludge in the French context. The scenarios were composed of one main process (incineration, agricultural land application, or landfill), one stabilization process (lime stabilization, composting, or anaerobic digestion) and transports of sludge. Average data on literature, real site data and simulation result were used for accomplishing the assessment. The indicator results of environmental impact were normalized by reference contributions of one person in the West-Europe over 1 year in order to better understand their relative magnitude. The normalization results were finally weighted to give one aggregated result of the comparative LCA with sensitivity analysis on the weighing factors. The study result showed: the combination of anaerobic digestion and agricultural land application was most environmentally friendly tanks to less emissions and less consumption of energy; the most important substances contributing to human toxicity and ecotoxicity were heavy metals released from the atmospheric effluent of incineration and from the sludge applied to agricultural fields; finally appropriate tools were required to control the non-point-source pollutants like the methane of the dispersed landfill gas and the effluent gases of transport vehicles.

Life cycle assessment of coal by-products based electric power production scenarios

Abstract In the next future coal will play an increasing important role in electricity production due to the abundant reserves worldwide. In order to design new production scenarios, environmental issues have to be carefully considered. We used Life Cycle Assessment (LCA) to compare, from an environmental point of view, six scenarios of electricity production by combustion of coal, coal cleaning by-products, biomass and petroleum coke, considering two existing combustion plants, de-NO x and de-SO x processes and coal ash valorisation options. The results showed that the more environmentally responsible scenarios include biomass co-combustion and gas treatment techniques and enlightened some options for further improvements. Finally the results confirmed the usefulness of LCA in the environmental innovation of industrial systems.

Evaluation of the potentialities to reduce greenhouse gases (GHG) emissions resulting from various treatments of municipal solid wastes (MSW) in moist tropical climates: application to Yaounde.

The authors here analyse the emission of greenhouse gases (GHG) resulting from the various treatment of municipal solid waste found in the town of Yaounde. Four management systems have been taken as the basis for analyses. System 1 is the traditional collection and landfill disposal, while in system 2 the biogas produced in the landfill is recuperated to produce electricity. In systems 3 and 4, in addition to the collection, we have introduced a centralised composting or biogas plant before the landfilling disposal of refuse. A Life Cycle Inventory (LCI) of the four systems was made; this enable us to quantify the flux of matter and of energy, consumed or produced by the systems. Following this, only the greenhouse effect was taken into account to evaluate the ecological consequences of the MSW management systems. The method used to evaluate this impact takes into consideration on the one hand, GHG emissions or avoided emission following the substitution of fuel with methane recovered from landfills or produced in the digesters, and on the other hand, sequestrated carbon in the soil following the regular deposit of compost. Landfilling without recuperation of methane is the most emitting solution for greenhouse gas: it leads to the emission of 1.7 ton of carbon dioxide equivalent (tCO2E) per ton of household waste. Composting and methanisation allow one to have a comparable level of emission reduction, either respectively 1.8 and 2 tCO2E/t of MSW. In order to reduce the emission of GHG in the waste management systems, it is advisable to avoid first of all the emissions of methane coming from the landfills. System 2 seems to be a solution that would reduce the emissions of GHG at low cost (2.2 to 4

An overall assessment of life cycle inventory quality - Application to the production of polyethylene bottles

/tCO2E). System 2 is calculated as the most effective at the environmental and economic level in the context of Yaounde. Therefore traditional collection, landfill disposal and biogas recuperation to produce electricity is preferable in moist tropical climates.

Case study of Yaoundé (Cameroon)

A qualitative, quantitative, and overall quality assessment of life cycle inventory is suggested. The method is composed of five indicators which are set up at three levels of the inventory quality: flows, processes, and the system. The method allows one to assess the reliability of the method generating inventory data (justness of data, completeness of data, representativity of processes, repeatability of system definition) and at the same time to quantify the uncertainty of the resulting data made under the data generation method. LCA practitioners can finally decide the overall inventory quality through the information for the acceptability of the inventory result comparing the objective of quality and the cost necessary to improve the quality. The operation of the method was verified in the application to the production of polyethylene bottles. The proposed method was also found applicable for the validation of data in the ISO’s LCA data documentation format.

A multi-criteria approach to evaluate the natural gas energy systems

The objective of the work is to evaluate the environmental impacts of municipal solid waste management systems in Yaoundé. Four management systems have been used as a basis for analyses. System 1 consists of traditional collection and landfilling without any pretreatment. In system 2, biogas generated by the landfill is recovered for electricity production. Systems 3 and 4 involve, after the waste collection stage, treatment by composting or anaerobic digestion respectively, followed by the dumping of refuse. Multicriteria analysis methods ELECTRE III and ELECTRE IS have been simultaneously applied to assess the four systems with respect to six environmental criteria. Results show landfilling with biogas recovery for electricity generation (system 2) appears as the most environmentally friendly management system.