Making the most of liquid digestate: Arkeale unveils a fertiliser of the future

The anaerobic digestion of food waste does not only produce biogas; it also generateshigh-valuedigestate. Whilst thesolid fractionis recognised for its ability to improve soil structure and provide long-term stabilisation, theliquid fraction remainsunder-utilised. 

Yet this liquid is a nutritional goldmine: rich in nitrogen (N), phosphorus (P) and potassium (K), it has the potential toreplace synthetic mineral fertilisers.  

It is to overcome the barriers to its use thatHélène Mastin,co-founder of Arkealeanda PhD student in biochemistry, has devoted her research to characterising this resource,in collaboration withINRAE. 

Understanding the variability of liquid digestates to make better use of them 

The study conducted by Arkeale and INRAE set outthree strategic objectives:

1. To characterise the variabilityof liquid digestates according to the origin of the inputs; 

2. To assess the impactof solid/liquid separation processeson thefinalquality;

3. To identify innovative ways of utilising the digestate, tailored to the needs of precision agriculture. 

Key findings from our research  

Through the analysis of 105 samples and advanced statistical analysis, we have identified three main categories of liquid digestate, based on their food waste content. Three key conclusions emerge: 

• Guaranteed safety:Liquid digestates have very low trace metal levels, allowing for safe and environmentally friendly application. 

• A specific nutrient profile:With a moderate nitrogen content but high levels of phosphorus and potassium, they are particularly well-suited to crops with low nitrogen requirements and to existing irrigation systems. 

• Expertise required:Unlike other types of digestate, the properties of liquid digestate vary considerably. Detailed characterisation is essential to optimise its effectiveness. 

Arkeale’s biochemical expertise in the service of the circular economy 

AtArkeale, we turn this complexity into an opportunity. Thanks to an innovative process involving filtration and biological acidification, we make liquid digestates more stable and effective, all without adding any external chemicals. 

We support our partners and clients in:

• Tailoringbespoke recovery solutions: fertigation, microalgae cultivation, hydroponics, etc. 

• Optimisethe integration of liquid digestates into circular and sustainable agricultural systems.