Small Breweries, Large Footprints? Environmental Implications of Brewing Waste

The rapid expansion of the craft brewing sector has increased the number of small breweries, leading to rising organically rich waste across aquatic, terrestrial and atmospheric ecosystems. Although brewery by-products are frequently discussed in terms of valorisation and resource efficiency, their environmental implications remain insufficiently examined. The present review synthesises current knowledge on waste generated by small breweries (i.e., operations with annual production volumes typically below 20,000 hL of beer), including their composition and management, with an emphasis on the potential environmental consequences of inadequate handling. Waste, including wastewater, solid by-products, gaseous emissions, odours, and noise, is considered, and their mechanistic effects on aquatic, terrestrial, and atmospheric compartments are discussed. Particular attention is given to cumulative and localised impacts in ecosystems, such as oxygen depletion, nutrient enrichment, altered microbial processes, and downstream effects on soil biota, aquatic food webs, and biodiversity. Commonly proposed mitigation and valorisation strategies are critically evaluated, with attention to ecological trade-offs and constraints related to scale, infrastructure, and regulatory thresholds. The review highlights a pronounced bias in the research literature towards chemical and toxicological characterisation, alongside a lack of field-based and long-term monitoring studies. By identifying key knowledge gaps and framing small brewery waste within an environmental context, this review emphasises the need for biomonitoring, scale-appropriate management approaches, and regulatory frameworks tailored to small breweries.