Plants and vegetables have already been successfully grown in a greenhouse in the international space station (ISS), which paved the way for building a greenhouse on the moon. Hydroponics and aeroponics are the methods of growing plants without soil, and they are highly likely will be adopted in a lunar greenhouse, because the regolith on the moon surface contains toxic perchlorates. Growing substrates are required for the hydroponic and aeroponic systems to hold the plants, and Rockwool is often used as a growing substrate (e.g. EDEN ISS, VEGGIE). However, Rockwool is not environmentally friendly and not healthy for human. This current study proposes to generate organic biodegradable growing substrates to support lunar greenhouses by recycling organic wastes. Organic wastes contain abundant cellulose since cellulose is the main component of plant cell walls, which allows cellulose to be a suitable material for supporting plant growth. Cellulose can be harvested from organic wastes via a chemical extraction, which involves steps of drying, grinding, extraction, boiling, bleaching. Cellulose can also be produced by bacteria, the organic wastes act as carbon and sugar resources for bacterial growth, and bacterial cellulose is produced during bacterial metabolism via the fermentation process. Harvested cellulose can be used as growing substrates to anchor the plants’ roots in hydroponic and aeroponic systems. Harvested cellulose can also be modified and 3D printed into plant containers. Cellulose is a biodegradable polymer and degrades away in a few weeks into sugar and water, therefore, there is no environmental burden of the used cellulose. Finally, converting wastes into useful resources on-site complies with space in-situ resource utilization strategy.
