Web-based participation has received growing interest over recent years. Such participation includes both profit- and non-profit-oriented sharing-economy initiatives. Not-for-profit sharing-economy initiatives focus less on economic aspects and more on awareness-raising in society regarding sustainability objectives (e.g. sustainable production and consumption of goods). In the current discussions around climate change and sustainable lifestyles, awareness-raising is important and new ways of reaching the public are attracting more interest. The question now is not simply to what extent non-profit sharing-initiatives achieve their goals, but how to assess any achievement as, due to the nature of these projects, little information on the participants’ background, perspectives and behaviour is available. These questions are discussed with reference to the Mundraub project, which allows people to share information on plants (e.g. fruit and nut trees, berry bushes and herbs) in public urban spaces (primarily German cities) so that others can harvest the plants for free. To learn about how sustainability objectives are achieved, data for the sites where the plants that have been mapped to Mundraub are located were analysed statistically. The results indicate that the people who are reached by the Mundraub project are mostly those who are already interested and aware of sustainability-related topics. The assessment approach used is a first attempt towards a better understanding of the extent to which the sustainability objectives of non-profit sharing-economy activities have been reached and towards identifying how the achievement of objectives might be improved on.