Anaerobic Digesters: What They Are & What They Do

Anaerobic digesters use a biological process used to manage some waste (like sewage, cow, pig, or chicken manure) and to produce a gas called “biogas.” Biogas is primarily composed of methane and carbon dioxide and depending on the waste feedstock and the system design is typically 55 to 75 percent pure methane (with some state-of-the-art systems claiming more than 95 percent pure methane).  Much of the industrial fermentation used to produce food and drink products uses anaerobic digestion.

Anaerobic digesters are categorized according to whether the biomass is fixed to a surface (called “attached growth”) or can mix freely with the reactor liquid (called “suspended growth”).  Digestors are also categorized by their organic loading rate and whether they are centralized or decentralized plants. Most anaerobic digesters are built as a “wet type” where the manure is mixed with water.  These can face challenges in areas where the processes use large quantities of water every day.  The other prominent type of digestor is called a solid-state digester.  These handle dry biomass and use gas-tight chambers called “fermenter boxes” that are loaded with biomass and manure.

Anaerobic digestion experts or consultants are those who have a significant background in the processes through education and/or experience.  Many have degrees in Civil or Environmental Engineering, Chemical Engineering, Biology, and specific expertise in related processes. These AD Experts should be experienced and familiar with solid-state anaerobic digesters (SSAD), submerged media anaerobic reactors, Sintex digesters, and a variety of batch systems and continuous stirred-tank reactors (CSTR). They should have a working knowledge of things like activated sludge processes, expanded-bed reactors, anaerobic lagoons, anaerobic migrating blanket reactors, and expanded granular sludge bed digestion (EGSB).  The Anaerobic Digestion expert may assist clients/investors in selecting the right Anaerobic Digestion technology and in preparing due diligence/feasibility studies and loan/grant applications.

During design, the Anaerobic Digester experts may perform a peer review of the design, prepare cost opinions and assist with permit applications.  During construction, the Anaerobic Digestion expert may assist with construction oversight of the facility and provide commissioning reports. They may also provide operator training, start-up assistance, and recipe management to assist in making the facilities run as smoothly and efficiently as possible. In matters involving Anaerobic Digestion litigation, the consultant may serve as an expert witness and assist the attorneys with understanding the processes and related technical issues and may testify in court about Anaerobic Digestion technology, economics, and related matters.

Large renewable energy and biochemical consulting firms certainly have experts in biotechnologies, as well as the more common areas like bio and renewable fuels, biomass, and biomass power, feedstocks, biomaterials, and biochemicals.  These larger groups will also have expertise in other technologies like agitation systems, anaerobic digestion, beverage fermentation, bio-oil extraction, bioreactors, carbon capture, carbon storage, carbonization, catalysis, cellulosic ethanol, cleantech, combined heat and power, direct combustion, enzyme technologies, fermentation, Fischer-Tropsch, gasification, genetic engineering, hydrothermal,  nanotechnology, organosynthesis, power generation, pyrolysis, renewable technology due diligence, synthetic biology, thermochemical conversion, torrefaction, water treatment, and waste management.

For over 25 years, Lee Enterprises Consulting has been assisting companies and investors with bioenergy, biofuels, biomaterials and chemicals, biotechnologies, and feedstock matters.   With over 150 consultants, we have the diverse expertise and geographical reach to assist in virtually any bioeconomy project worldwide. These seasoned professionals average over 30 years of industry experience.  Our ability to assemble these professionals into multidisciplinary teams allows us to fully integrate the technical, scientific, and regulatory aspects of a project, and combine them with years of hands-on experience.  Take a look at our experts and the services we provide.  You will note that most of our experts are also available for ancillary engagements and advice, for specialty engagements like serving as expert witnesses in litigation matters.  Call us at 1+ (501) 833-8511 or email us for more information. See  Design Realities for Anaerobic Digestors.