PGS (Participatory Guarantee System) is an alternative certification system to third party certification where farmers, sometime together with consumers, organised themselves and become the owner of the certification system. PGS is an example of an institutional innovation that offers a systemic approach towards sustainable agricultural production suitable for small-scale farmers. As alternative certification methodology, PGS expands the horizon of guarantee systems in order to include in the value chain various stakeholders: producers, consumers, retailers, traders and others, such as NGOs.

PGS builds long-term trust-based relationships and accelerates learning processes through a more efficient and equal access to knowledge. Thus, it is a form of grassroots innovation that addresses social needs, but also contributes to economic and environmental sustainability. Creating a platform for social relationships and knowledge-exchange, PGS provides adaptable and localized services in situations where the market is usually failing.