Sign Up Early for SB'24 San Diego and Save! Spring Rate Ends June 23rd.

Waste Not
Understanding Digestate:
The Bounty from Anaerobic Digestion

Leveraging the potential of anaerobic digestion and utilizing digestate as a renewable soil amendment offers significant opportunities for sustainable and regenerative agriculture.

As the global population continues to grow and land resources become increasingly limited, agriculture faces significant challenges. In response, there has been a shift towards sustainable practices in agriculture — such as organic farming, agroecological methods, and eco-friendly solutions are being embraced, all with an eye on sustainability. At the forefront of this transformation is anaerobic digestion and the use of digestate in agricultural soils.

Harnessing digestate for sustainable agriculture

Anaerobic digestion is a natural process that occurs in the absence of oxygen. It is similar to the decomposition process in a compost heap but takes place in a fully enclosed environment without air. In this specialized setting, microorganisms — particularly bacteria — work to break down often-wasted organic matter including food scraps, agricultural residues, wastewater sludge and other byproducts of harvesting food crops. This process produces biogas — which is primarily composed of methane and carbon dioxide and can be used as a clean, renewable energy source. Anaerobic digestion also generates digestate — a nutrient-rich, organic fertilizer similar to compost. This closes the loop by turning previously wasted resources, whose degradation exacerbates climate change, into valuable resources — creating a truly circular solution for farmers and food producers.

Digestate plays a crucial role in the ecological cycle. Unlike traditional compost, digestate is characterized by its high nutrient content — which can enrich soil and improve agricultural productivity. When used as an organic soil amendment, it promotes better plant growth and enhances soil vitality. By repurposing and reutilizing organic waste, digestate exemplifies a holistic approach to sustainability.

One of the most significant advantages of digestate is its nutrient composition. All the nitrogen, phosphorus and potassium from the original feedstocks are retained in digestate; this makes it a superior alternative to synthetic fertilizers derived from fossil fuels — offering numerous benefits for both agriculture and the environment.

Environmental benefits of embracing digestate

Unlike synthetic fertilizers, which require substantial energy for production and often rely on natural gas, digestate offers a sustainable alternative. By harnessing organic waste and microbial activity, digestate production significantly reduces energy consumption and carbon emissions associated with fertilizer production — reducing reliance on fossil fuels and mitigating methane emissions from the reutilized feedstock.

Why digestate excels as a soil amendment

Digestate is more than a byproduct; it optimizes crop production and sustainability. Its benefits over conventional fertilizers include:

  1. Instant nutrient availability: With a little over 70 percent water content, digestate doesn't need additional moisture to be ready for plants. It is readily available for absorption, providing fast results. In contrast, dry fertilizers require additional water to dissolve into a usable form.

  2. Comprehensive nutrient mix: Anaerobic digestate, often called "rocket fuel" for crops, is essential because — just as our bodies need multiple vitamins and minerals to absorb calcium — crops require a range of nutrients to maximize growth. In addition to phosphorous and potassium, digestate contains sulfur — which enhances plants' nitrogen absorption.

  3. Soil health: Digestate boosts soil health and quality. Unlike chemical fertilizers, which provide a limited range of nutrients, digestate includes a well-rounded mix that also contains organic matter — which conditions the soil, maintains fertility, improves structure, and further replenishes organic matter.

Leveraging the potential of anaerobic digestion and utilizing digestate as a sustainable soil amendment offers significant opportunities for agriculture and environmental stewardship. By adhering to quality standards and adopting responsible land-management practices, we can fully exploit digestate's potential to reduce our carbon footprint, promote energy efficiency, and cultivate a more resilient food system for the future. Embracing digestate as a renewable soil amendment is a crucial step toward a literally greener and more sustainable future.