Aquaculture 2022

February 28 - March 4, 2022

San Diego, California

CHALLENGES TO ANAEROBIC DIGESTION OF WASTE STREAMS FROM LAND-BASED RECIRCULATING AQUACULTURE SYSTEM (RAS) FACILITIES

Abhinav Choudhury1*, Christine Lepine1, Freddy Witarsa2,

and Christopher Good1.

 

1The Conservation Fund Freshwater Institute,

Shepherdstown, WV, USA 25443

2Colorado Mesa University,

Department of Environmental Science and Technology,

Wubben Hall and Science Center,

Grand Junction, CO, USA 81501

 

achoudhury@conservationfund.org

 



Land-based recirculating aquaculture systems (RAS) have led to increased fish production efficiencies through increased stocking densities and have the additional benefit of capturing environmentally harmful concentrated sludge from fecal matter and uneaten feed. In addition to waste sludge production, land-based RAS facilities can also generate unintentional fish mortalities. Furthermore, on-site processing of harvested fish can produce waste offal (e.g., heads, guts, scales, bones) that can be up to 40% of the original fish weight. Anaerobic digestion (AD) is a sustainable and effective means of organic waste treatment in the dairy, swine, and wastewater treatment industries. In the absence of oxygen, microorganisms break down organic matter and produce biogas, a mixture of methane and carbon dioxide, which can then be used for renewable energy production. The AD process also results in the formation of a nutrient-rich liquid fertilizer with a reduced solids content. Research on the waste treatment of RAS sludge is still in its infancy, and AD could be a potential solution to this issue. There has been some research on the anaerobic co-digestion of fish offal mixed with other organic wastes, but the results have been variable. Challenges to operational and process stability still need to be addressed. Sludge from RAS facilities, mortalities, and fish offal, utilized as AD substrates, can significantly influence the operational and process parameters in a digester, such as, alkalinity, total ammonia nitrogen, long-chain fatty acid and volatile fatty acid concentrations, carbon/nitrogen ratio, organic loading rates, hydrogen sulfide concentrations, salinity, and pH. Understanding the impacts of these waste streams on the aforementioned parameters is vital for gauging the feasibility of AD as a potential sustainable waste treatment technique for land-based RAS facilities. This presentation will discuss specific concerns associated with the digestion of these waste streams (sludge, mortalities, offal) from RAS facilities and potential solutions to address these issues.