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 a