Biorresiduos

Biowaste is the biodegradable fraction of municipal waste, mainly food, kitchen and garden (pruning) waste. It accounts for a large share of municipal solid waste (MSW) in Spain and the EU, commonly around a third and by some estimates up to 40%, which makes it a key fraction for meeting European recycling targets.

Managing it properly reduces the environmental impact of landfills, where it generates methane, a greenhouse gas with a global warming potential roughly 28 times that of CO2 over 100 years according to IPCC AR6. It also allows biowaste to be used as a resource, producing compost or biogas.

Legal definition

Spain's Law 7/2022 on waste and contaminated soils for a circular economy defines biowaste as biodegradable garden and park waste, food and kitchen waste from households, restaurants, caterers and retail premises, and comparable waste from food-processing plants. It covers both domestic waste and waste from commercial and industrial food activities.

Composition of biowaste

• Food waste: fruit, vegetables, meat, fish, bread, dairy.
• Kitchen waste: coffee grounds, eggshells, used napkins.
• Garden and pruning waste: leaves, branches, grass.
• Other biodegradables: small pieces of untreated wood.

Its composition varies with the season, consumption habits and whether the setting is urban or rural.

Legal framework

At European level

• Directive 2008/98/EC (Waste Framework Directive).
• Directive (EU) 2018/851, which required separate collection of biowaste by 31 December 2023.

At national level

• Law 7/2022, which brought forward the obligation of separate collection for all Spanish local authorities.
• Regional waste management plans, which set specific strategies for the organic fraction.

Biowaste collection systems

Brown bin

• A dedicated fraction for organic matter.
• Identified by its brown colour, using compostable bags.
• Increasingly rolled out in large cities such as Madrid, Barcelona and Valencia.

Door-to-door collection

• Used in small municipalities and some urban areas.
• Organic waste must be handed over on specific days.
• Improves the quality of the collected waste.

Home and community composting

• In rural and peri-urban areas, biowaste can be managed in individual or community composters.

Large generators

• Restaurants, markets and supermarkets must separate biowaste for dedicated collection.

All of these approaches rely on good separate collection to keep the organic stream clean.

Treatment of biowaste

Composting

An aerobic biological process that turns biowaste into compost, an organic fertiliser. Benefits include improved soil, substitution of chemical fertilisers and the return of nutrients to the natural cycle.

Anaerobic digestion

Anaerobic digestion takes place without oxygen and produces biogas (methane and CO2) and digestate. The biogas is used to generate electricity and heat or is injected into the grid, while the digestate can be used as an agricultural fertiliser.

Energy recovery

Part of the biowaste that is unsuitable for composting or digestion is sent to incineration with energy recovery.

Benefits of correct management

1. Environmental: less landfill methane, lower leachate contamination and recovery of soil nutrients.
2. Economic: savings on landfill and incineration costs, revenue from compost and biogas, and green jobs.
3. Social: stronger citizen participation, a better image for sustainable municipalities and environmental education.

Risks of poor management

• Higher methane emissions in landfills.
• Formation of contaminating leachate.
• Loss of usable nutrients.
• Penalties for non-compliance with European rules.

Biowaste and the circular economy

Biowaste is one of the clearest examples of the circular economy applied to waste, in line with the waste hierarchy. It is turned into compost and biogas, closing the loop of organic matter, reduces dependence on fertilisers and fossil fuels, and creates jobs in both rural and urban areas.

Conclusion

Biowaste is one of the most important waste streams and one with the greatest potential for recovery. Its correct collection and treatment is key to reducing greenhouse gas emissions, recovering nutrients and advancing towards a circular economy. In short, biowaste should not be seen as rubbish, but as a strategic resource for environmental, economic and social sustainability.

At Manglai we help companies measure their carbon footprint and prepare their sustainability reporting, including the impact of their organic waste. Discover how Manglai can help you.