28th April 2016, Aqua Enviro Events Suite, Wakefield
Digestate Dewatering – Overview
De-watering is an essential first step in valorisation or further treatment of anaerobic digestates – whether in the waste water, waste or farm-fed AD sectors. This one day event aims to present the current state of the art in de-watering, with a particular focus on commercial and near-commercial approaches to managing food-based and crop/slurry-based digestates.
Whether you are an AD operator, digestate contractor or researcher this conference provides an opportunity to learn, share and shape the future of digestate management in the UK.
Please download the full event brochure to view the detailed programme/speakers.
Following several years of remarkable growth, the UK anaerobic digestion (AD) sector now faces a number of significant challenges – particularly around security of feedstock supply (and price) and energy revenue. Digestate is usually the forgotten piece of the jigsaw, with third party contractors willing to take the material away for around £10 per cubic metre. For a 30kt AD plant, this can mean digestate disposal costs in excess of £250,000 a year. Reducing these costs is an increasing focus in the sector, although the ultimate aim is to convert digestate from a cost centre to a revenue centre.
Many attempts to address this aim have been made over the past decade, with suggestions varying from liquor digestate as a substrate for algae production to fibre digestate as a constituent in growing media / composts. One promising approach has already been demonstrated for farm-fed AD systems, with soluble phosphorus precipitated and subsequently recovered in the separated fibre fraction. The resulting liquor fraction is subjected to ammonia stripping and the final effluent used instead of clean water to dilute incoming feedstock at the start of the process. The success of this approach and virtually all others hinges on the de-watering step.
The surface charge properties of food-based digestates make them challenging to de-water using standard approaches, such as those used to de-water sludge in the waste water treatment sector. While de-watering of food-based digestates has proven possible through selection of the correct polymer, polymer dose and dosing conditions – the economics remain challenging.
Aqua Enviro invite you to attend this event in which we plan to explore the following themes:
1. Current approaches to de-watering food-based and crop/slurry-based digestates, including the economics and impacts on nutrient partitioning;
2. Near market approaches to de-watering food-based and crop/slurry-based digestates;
3. Challenges associated with de-watering of different substrates and the impacts of mesophilic vs thermophilic digestion.