Urban Agriculture and Compost: Revitalising Degraded Urban Soils

Soil degradation remains a significant factor contributing to food insecurity and ecological instability across Africa. Unsustainable agricultural practices, including overgrazing and conventional farming techniques, rob the land of its nutrients, drastically reducing annual production capacity. As urban areas continue to expand, the degradation of soils accelerates, making the need for effective restoration strategies more urgent.

Composting has emerged as a crucial tool in stimulating microbial activity and improving soil structure, enabling farmers to combat these challenges. The impact of urbanization, characterized by concrete structures and population density, exacerbates soil degradation, necessitating innovative solutions to restore urban agricultural land.

The Loss of Urban Agricultural Land Is Dire

According to United Nations data, over two-thirds of Africa’s productive land is degraded, with desertification affecting around 45% of the total land area. Moreover, the continent loses approximately four million hectares of forest each year, further exacerbating the issue. Soil deterioration is not only a local problem; it is also a critical driver of climate change. As soil structure breaks down due to erosion and arid conditions, the carbon stored in the soil is released into the atmosphere, contributing to greenhouse gas (GHG) emissions. Degraded land is less resilient to extreme weather events, making it more vulnerable to flooding and droughts.

The alarming rate of degradation up to 100 times faster than the natural replenishment of nutrients has led to immense losses in crop yields. Unmanaged runoff is also a major contributor to field waterlogging, further impeding plant growth. Collectively, African farmers face an estimated loss of $68 billion due to the diminishing productivity of increasingly degraded croplands.

Benefits of Composting in Urban Soil Restoration

The biochemical transformation of organic material into compost through microbial activity plays a vital role in addressing soil degradation in Africa. Composting not only minimizes waste but also fosters biodiversity, which is critical for urban agriculture and ecosystem resilience.

Enhanced Soil Structure

The application of compost can significantly improve soil texture by promoting aggregation and porosity. This enhanced soil structure facilitates better aeration and water infiltration rates, while also mitigating compaction a common challenge in urban environments where soil is frequently disturbed. By integrating compost into urban landscaping and agriculture, the physical properties of the soil are improved, creating a conducive environment for plant growth.

Increased Soil Organic Matter

Well-cured organic compost stabilizes and enhances nitrogen levels and organic matter within the soil. This process improves the root environment, leading to increased vitality and accelerated growth rates, ultimately boosting crop yields. Additionally, compost application reduces reliance on chemical fertilizers, which can contribute to harmful runoff and further soil degradation.

Improved Water Retention

Compost-enriched soils demonstrate a superior capacity for retaining moisture and oxygen. Research indicates that even a 1% increase in organic matter can enable soil to retain up to 20,000 gallons of water per acre. This improved moisture retention is vital not only for plant growth and yield but also for promoting water conservation a crucial aspect of urban revitalization and sustainability.

Soil Fertility and Nutrient Cycling

Organic compost acts as a slow-release fertilizer, reintroducing essential microbes, such as mycorrhizal fungi and nitrogen-fixing bacteria, into soils that have been depleted by conventional farming practices and pesticide use. This enhancement of microbial life improves nutrient uptake in plant roots, providing resilience against pathogens.

Municipal Waste Management

Composting can substantially reduce the amount of organic waste that ends up in landfills. For instance, officials in Addis Ababa, Ethiopia’s capital, are making significant strides in leveraging composting to manage waste effectively. Despite the fact that less than 10% of the city’s waste is currently composted, the ongoing initiatives signify a positive direction towards establishing a more sustainable urban agricultural framework.

Economic Viability

In economically challenged urban areas, composting can substantially reduce input costs. By utilizing readily available organic waste, farmers can produce their own nutrient-rich plant food, decreasing their dependence on expensive chemical fertilizers. This approach is particularly beneficial for cities with a high population of smallholder farmers. For example, in Maputo, Mozambique, community composting initiatives empower local farmers to sustainably enhance soil fertility.

Composting and Sustainable Urban Development

Applying organic matter to urban soils is a proven method for improving soil structure and enhancing carbon sequestration. This solution has the potential to significantly restore urban land while also minimizing GHG emissions.

However, composting is not without its challenges. Critics often point to the organic matter decomposition process, which can release GHGs into the atmosphere and increase disease risk. Moreover, the composting process can be slow, leading to a reliance on chemical fertilizers to meet rapidly growing food demands.

Regardless of these challenges, the benefits of composting are clear. There has been a renewed interest in the practice, signaling a shift towards more sustainable urban agriculture. Future developments should focus on introducing advanced processing facilities in cities and incentivizing farmers to adopt composting practices.

The Growing Popularity of Africa’s Urban Soil Composting

As urbanization accelerates and food insecurity escalates, there is a growing investment in sustainable composting solutions by both governments and individuals. This trend is rapidly gaining traction across the continent, yielding promising results.

In Nairobi, for instance, the Norwegian Investment Fund Norfund has financed projects aimed at developing organic fertilizers and composting to promote a more circular economy. These programs have achieved remarkable success, upcycling 60,000 tons of waste and reducing carbon emissions by 50,000 tons. Such initiatives not only improve urban soil health but also enable residents to cultivate vegetables and fruits in community gardens.

In the Benin Republic, farmers have begun composting unused organic waste from households and crops as a response to chemical-induced soil infertility. This practice aims to expand access to agricultural facilities while combating the effects of drought and flooding, which have threatened food supplies in urban areas. By improving the soil’s water-holding and filtration capacity, composting equips communities to better withstand the impacts of climate change.

Revitalising Africa’s Degraded Urban Land

Composting stands out as a transformative practice for urban land restoration in Africa, offering a sustainable alternative to chemical fertilizers while enhancing soil health and resilience. The multifaceted benefits of composting underscore its critical role in addressing the challenges posed by urbanization and climate change. With appropriate investments and supportive policies, composting practices could become the standard for ensuring food security for growing urban populations.

Conclusion

The pressing need to revitalise degraded urban soils in Africa calls for a concerted effort to integrate composting into urban agriculture. This practice not only addresses the immediate challenges of soil degradation but also contributes to long-term sustainability, economic viability, and food security. By fostering collaboration between local governments, communities, and private sectors, African cities can transform waste into valuable resources, ensuring healthier soils and more resilient ecosystems for generations to come.

As urbanization continues to reshape the continent, the potential of composting as a sustainable agricultural practice cannot be overlooked. It represents an opportunity to not only restore degraded urban land but also to empower communities, enhance food production, and contribute to a healthier environment. Through continued commitment and innovation, composting could pave the way for a greener, more sustainable future for urban agriculture across Africa.