For anaerobic digestion and biogas plants — digestate treatment
Digestate from anaerobic digestion contains high concentrations of ammonium nitrogen and phosphorus, and finding outlets for it as liquid fertilizer or treating it as wastewater is a burden. We are researching technology that takes up the nitrogen and phosphorus in digestate with microalgae and recovers them as algal biomass.
Talk to us about this industryCurrent stage
Research stage (seeking lab-evaluation and validation partners)
The literature shows that digestate is dark and high in ammonia, so algae struggle to grow in it as is. We are at the stage of lab-evaluating suitability digestate by digestate, and are seeking plant operators for joint validation. The digestion process itself is not changed.
Challenges in this industry
Finding outlets for digestate
Land and seasons for spreading it as liquid fertilizer are limited, creating storage and transport burdens.
Energy and cost of nitrogen treatment
Treating high concentrations of ammonium nitrogen takes energy and money.
Regional nitrogen surplus
In livestock regions and elsewhere, excess nitrogen contributes to eutrophication of water bodies.
What Novelgen can offer
Digestate suitability evaluation
In the lab we evaluate whether algae grow in your digestate, including dilution and pre-treatment conditions.
See details →Assimilating and recovering nitrogen and phosphorus
Algae take up ammonium nitrogen as amino acids, so nitrogen is retained as a resource rather than lost to the atmosphere.
See details →Turning recovered algae into resources
We also look at using recovered algae as feed or fertilizer feedstock.
See details →Evidence and public information
Microalgal cultivation on digestate and nutrient removal from it have been reviewed in peer-reviewed literature. Reviews report that high ammonia, turbidity and colour are the main inhibitors, that dilution, pre-treatment and strain selection can mitigate them, and that carbon sources from biogas plants can raise algal production.
References
- Xia A., Murphy J.D. Microalgal Cultivation in Treating Liquid Digestate from Biogas Systems. Trends in Biotechnology, 2016, 34(4), 264–275. doi:10.1016/j.tibtech.2015.12.010
- Al-Mallahi J., Ishii K. Attempts to alleviate inhibitory factors of anaerobic digestate for enhanced microalgae cultivation and nutrients removal: A review. Journal of Environmental Management, 2022, 304, 114266. doi:10.1016/j.jenvman.2021.114266
- Chong C.C., et al. Anaerobic digestate as a low-cost nutrient source for sustainable microalgae cultivation: A way forward through waste valorization approach. Science of the Total Environment, 2021, 803, 150070. doi:10.1016/j.scitotenv.2021.150070
- Stiles W.A.V., et al. Using microalgae in the circular economy to valorise anaerobic digestate: challenges and opportunities. Bioresource Technology, 2018, 267, 732–742. doi:10.1016/j.biortech.2018.07.100
How a PoC works
- STEP 1
Discovery
We learn about your feedstock, throughput, and how you currently dispose of digestate and at what cost.
- STEP 2
Lab suitability evaluation
We confirm algal growth and nitrogen/phosphorus uptake using a digestate sample.
- STEP 3
Pre-treatment and dilution conditions
Where needed, we study dilution and pre-treatment and cultivate at small scale.
- STEP 4
Validation plan
We plan an on-site pilot including use of the recovered algae.
What to prepare
- A digestate sample
- Analysis data (ammonium nitrogen, total nitrogen, total phosphorus, COD, SS, colour, pH, etc.)
- Digester feedstock (food waste, livestock manure, sewage sludge, etc.)
- Digestate volume and your current disposal method and cost
- Available land and whether waste heat is available
Frequently asked questions
- Can digestate be treated as is?
- Digestate is generally high in ammonia and turbidity, and dilution or pre-treatment is considered necessary. Conditions differ by digestate, so we determine them through sample evaluation.
- Do you have a track record?
- This is currently at the research stage. We accept joint validations starting from lab suitability evaluation.
- Will it affect biogas yield?
- Our scope is treating digestate after digestion; the digestion process itself is not changed.
- What happens to the recovered algae?
- We look at turning them into feed or fertilizer feedstock.
- Can the plant’s waste heat or CO₂ be used?
- The literature reports that waste heat can be used for culture temperature control and that carbon sources from biogas plants can support algal production. We assess this against your site conditions.
Note: this page is an overview based on public information. Technical details such as strains, cultivation conditions and individual test data are shared after a non-disclosure agreement (NDA) is signed.
Related pages
Aquaculture & seedling production
Stable supply of feed microalgae and land-based short-term fattening of oysters and other bivalves.
Agriculture & fertilizer
Co-development of fertilizer feedstock and soil amendments from algal biomass.
Industrial wastewater
Purify nitrogen- and phosphorus-rich industrial effluent with algae and recover it as a resource.
Talk to us about digestate treatment
Tell us about the characteristics of your digestate and how you dispose of it today. We will explain how a lab evaluation works.
Talk to us about this industry