Photoreforming of food waste into value-added products over visible-light-absorbing catalysts

Abstract

Approximately 1.3 billion tons of food waste are generated each year, resulting in societal, economic and environmental repercussions across the globe. While efforts to minimise losses and redistribute resources are underway, vast quantities of food waste must still be managed. Photoreforming offers a simple, sunlight-driven method for transforming food waste into valuable chemicals and clean H₂ fuel, but the minimal previous research on this topic relied on expensive and UV-absorbing catalysts. Here, we utilise two precious-metal-free and visible-light-driven photocatalytic systems (CdS quantum dots in alkaline solution and carbon nitride with co-catalyst Ni₂P under pH neutral conditions) to photoreform a variety of carbohydrates, fats, proteins and real-world mixed wastes into H₂ and organic products such as formate. CdS offers higher efficiencies in alkaline media than a benchmark TiO₂|RuO₂-Pt catalyst, but carbon footprint calculations suggest that photoreforming with carbon nitride|Ni₂P in pH neutral H₂O offers a more sustainable route towards real-world application.