*4.4. Discussion*

The research question for the present study was: "How can a public school in the RMPF of the state of Rio de Janeiro, Brazil, act as a voluntary delivery point and support the development of a reverse supply chain for waste cooking oil?" In order to answer that question, we developed an action plan based on the integration of actors and efforts. The local government, through the secretaries of education and environment and the water and sewer treatment company, could provide some incentives for school management, teachers, students, the PTA, and the community to foster acceptance of the idea of WCO collection and recycling.

At the same time, as a VDP, the school needs to be integrated into the WCO reverse supply chain, connecting household generators with collectors. One important issue is the logistics of this integration. Environmental education is an important tool for teaching the community how to appropriately store WCO that is of good quality and also to convince them to take WCO to the school´s VDP.

Regarding the WCO reverse supply chain, the results show the importance of establishing contracts between commercial generators and collection cooperatives/companies, with price incentives for volume and quality, appropriate storage conditions, the frequency of generation, and avoiding exchange for cleaning products (soap) that don't meet environmental standards.

The collection cooperatives/companies should also use routing systems with enough vehicles that are managed by trained personnel, in order to minimize logistics costs. In addition, the biodiesel industry should adopt more proactive behavior, coordinating the chain and establishing a strong relationship with recycling cooperatives and companies, to ensure a continuous supply of WCO.

In addition, the local governmen<sup>t</sup> should play a role in the WCO reverse supply chain, primarily: regulating the actors with incentives (tax) and controls; formalizing self-employed informal collectors by integrating them into existing cooperatives/associations; preventing soap production that does not follow environmental standards; maintaining the continuity of environmental education programs, along with WCO collection, in order to foster the development of more environmentally friendly citizens and reduce the cost of water and sewer treatment.

The results of the present study are in line with the literature review. Waste managemen<sup>t</sup> related to WCO involves non-generation, reduction and recycling [23]. In order to accomplish this, the reverse supply chain needs to work well in terms of organization, cost efficiency and value generation [9], integration of small- and large-quantity generators [29], and adequate storage conditions [30]. Voluntary delivery points are strategic for collecting WCO from households (small-quantity generators) [11], without neglecting the importance of route planning to keep logistics costs down [32].

The idea of generating an action plan is also related to the National Solid Waste Policy, which demands a Municipal Plan of Integrated Solid Waste Management with shared responsibility among generators, collectors, recyclers and industry, and social inclusion of individual collectors in cooperatives and associations [13,22,24,25].

However, since there are no specific regulations for WCO reverse logistics [7], environmental education in schools is an important strategy to compensate for that gap. It is important to insert this issue across school subjects and curricula [42,45] Several other factors are also important: involvement of the community in school activities [51,52]; presenting information about the cost of collective selection programs and the convenience of VDPs [41]; highlighting biodiesel as the main product generated from WCO [37,38]. It is hoped that such programs will generate citizen awareness of ways to dispose of WCO appropriately [41,50].
