Automatically Fed Digesters
Anaero Technology’s lab-scale anaerobic digestion research bioreactors are capable of automatically feeding heterogeneous feedstock, as used in full-scale AD operation. This system provides high quality replication of full-scale AD processes, from feed storage, to digestate capture in a gas-tight set (feeder, digester, digestatetank, gas flow meter) that allows efficient mass balances.
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Feed as often as required with our range of automatic feeders capable of accurate delivery of small volumes of mixed slurries. We have used mixed feed (19%DS avg) entering a full-scale FW AD plant in our feeders for over 8 years and successfully replicated the operation of full-scale digesters to solve problems such as foaming, inhibition, optimal loading, effect of new substrates, and trace element supplementation; where manual feeding previously skewed results.
The feed dispensing pump provides storage for several days. Feeding once a day causes transient organic shock to digesters and limits the OLR achieved at the lab compared with OLRs at full-scale where feed is more discrete. Automatic feeding saves daily visits to the lab because the feeder needs topping up once or twice a week. Since feed dynamics is determining of processes (overfeeding can cause foaming, acidification, shock,; underfeeding low biogas, higher CH4, higher pH ,etc.), research using automatic feeding is more representative of real life and can open the way to new developments in AD and fermentation.
Use real feed
Sourcing, processing, and storing feed samples can be challenging and impact smooth research under controlled conditions if a feed batch finished before observations are complete and new feed batches need to be used. While peristaltic pumps block with the smallest particle, our feeders are accurate and consistent even for mixed, slurry substrates. Our auto-feeder systems have been operating on AD plant food waste, as it enters full-scale digesters at around 19%DS for over 8 years and successfully worked up to 36%DS mixtures of food waste and waste flour.
Although our main feeders not suited for fibrous material, such as energy crops, small amounts of fibrous material have been successfully co-digested using them (straw and pulp paper mash <5% of ds). We also have a dry solids auto-feeder under development. The ability to automatically feed real, not synthetic, or dilute, feed adds significance to research on mixed feedstock, such as food waste, STW sludges, and slurry, etc. For settleable feedstock, our feeders have online agitators that homogenise the feed as it is being delivered to the digesters.
Flexible Process Configuration
Enzymic hydrolysis and acid-phase digestion have evolved largely through costly pilot-scale studies and once at full-scale the pressures of operational regimes limit further experimentation and optimisation. For example, the limited reliable research on biological hydrolysis and multi-stage digestion, could account for the relatively low uptake and high cost,. Scale-down research reactors capable replicating the conditions of multi-stage systems in continuous mode are not widely available.
Novel prodcuts and optimised processes, such as hydrolysis-AD, Hydrogen-CH4, biochemical factory-
AD gas on demand, optimised agronomic properties of digestate, and others, present significant research interest and could benefit from equipment capable of feed regime control multiple physical-chemical conditions in batch or continous mode, alternation of conditions such as acidification, hydrolysis, pasteurisation, thermophilic, mesophiic, psychrophilic, hyper-thermophilic, supplementation, etc. "high value" chemicals, microbiology and metabolite dynamics of AD processes, antibiotics and nutrients, have become important topics of research.