Agriculture plays a key role in the transition to circular economy on a tropical island

Kleinpeter Vivien, Vayssières Jonathan, Degenne Pascal, Choisis Jean Philippe, Wassenaar Tom, Lo Seen Danny, Vigne Mathieu. 2021. Agriculture plays a key role in the transition to circular economy on a tropical island. In : 2021 International Conference on Resource Sustainability - Book ok abstracts. icRS, University College Dublin, Failte Ireland. Dublin : icRS, 215-218. 2021 International Conference on Resource Sustainability (icRS2021), Dublin, Irlande, 19 Juillet 2021/23 Juillet 2021.

Résumé : Several tropical islands have a high and growing human population that fuels two conflicting dynamics: an increasing need in food and a decreasing availability in agricultural lands due to urban sprawl. Pushed by resource and land limitations, some islands including Réunion choose to both import human food and set up high-input agricultural production systems that rely on imports of mineral fertilisers and raw materials for animal feed. This globalised agrifood system has numerous negative externalities such as nutrient surpluses (and corresponding risk of soil and water pollutions), resources depletion (phosphorus and nonrenewable energies) and greenhouse gas emissions due to transportation. A transition to a circular economy (CE) can potentially increase the island autonomy, partially mitigate these negative externalities and foster local economic development. Biomass-based CE is particularly relevant for tropical volcanic islands, like Réunion, endowed with rich soils and higher crop yields. We studied the opportunities associated with biomass produced locally and used or usable as agricultural inputs to increase circularity within Réunion. The methodology used was based on a material flow analysis (MFA) coupled with a multi-stakeholder participatory approach. It was applied to the present agri-food system to identify local initiatives contributing to the transition to a CE. Results of the MFA show that 585 000 tons dry matter (tDM) of biomass used or usable as agricultural inputs are produced in Réunion. The agro-industry sector is predominant, representing 58% of the production. 325 000 tDM are used in agriculture (83 %) or urban sectors (4%), or eliminated (landfill site or discharge to the sea) (13%). The difference (260 000 tDM) corresponds to important atmospheric nitrogen and carbon emissions due to intermediary processes like composting and biomass combustion to produce electricity. This MFA leads us to identify three main levers to increase circularity at territorial level: i) A large part of eliminated materials could be used in agriculture, e.g. urban biowaste as fertilizer, food industry waste as animal feed; ii) Atmospheric emissions could be reduced to increase nutrient conservation and carbon sequestration; iii) The efficiency of agricultural processes at both plot and herd levels could be increased by better matching available inputs (fertilizers and feeds) with plant and animal needs. Results of the participatory approach show that the main stakeholders of the agri-food system in La Réunion (farmers, cooperatives, industrials, energy producers, public and private waste management organisations) are already involved in the transition to a CE. Several on-going industrial symbiosis initiatives were identified and four are in the design phase: 1. a whole-island fodder supply chain with collective fodder storage units to increase local fodder use, 2. manure spreading plans to reduce manure transport distances for each livestock farmer, 3. collective platforms to co-compost urban green waste with manure to produce organic fertilisers for market gardeners, 4. a door-to-door collection of households biowaste and anaerobic digesters to produce bioenergy. In conclusion, agriculture plays today a key role in the transition to a CE in Réunion. The research is now continuing with a Substance (nutrients) Flow Analysis (SFA) and an Ecological Network Analysis (ENA) of the whole island economy, i.e. between all economic sectors, including imports, exports, and atmospheric emissions. The objective is to assess the efficiency and the integration of the different sectors, including agriculture. An integrated spatially explicit simulation model is also under-development to study the potential (positive or negative) synergies between the four symbiosis initiatives in the design phase to better access their consequences on circularity, and environmental and economical efficiencies.

Auteurs et affiliations

• Kleinpeter Vivien, CIRAD-ES-UMR SELMET (REU)
• Vayssières Jonathan, CIRAD-ES-UMR SELMET (REU) ORCID: 0000-0003-3127-7208
• Degenne Pascal, CIRAD-ES-UMR TETIS (FRA)
• Choisis Jean Philippe, INRAE (FRA)
• Wassenaar Tom, CIRAD-PERSYST-UPR Recyclage et risque (FRA) ORCID: 0000-0002-0098-5503
• Lo Seen Danny, CIRAD-ES-UMR TETIS (REU) ORCID: 0000-0002-7773-2109
• Vigne Mathieu, CIRAD-ES-UMR SELMET (MDG) ORCID: 0000-0003-1543-9043

Source : Cirad-Agritrop (https://agritrop.cirad.fr/604055/)

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