Enhanced biogas production from nitrogen bearing feed stocks

Abstract

A system comprising a first anaerobic digester (12), an ammonia recovery vessel (16) and a second anaerobic digester (14). Microorganisms in the first digester are primarily hydrolyzers and acetogens, while those in the second digester are primarily methanogens. A nitrogen containing feed stock undegoes hydrolysis ans acetogenesis in the first digester. The effluent is passed to the ammonia recovery vessel in which ammonia is removed. The low ammonia effluent stream is passed to the second digester to undergo methanogenesis, generating a biogas. In an alternate embodiment, a single anaerobic digester is used. The effluent is treated for ammonia removal and recycled to the digester to keep the ammonia levels sufficiently low to avoid ammonia inhibition.

Description

Background technique [0001] This invention relates to the anaerobic treatment of feedstocks to produce biogas, and more particularly to the anaerobic treatment of nitrogenous feedstocks to produce biogas. [0002] Over the past few decades, a great deal of scientific and engineering work has been done on the biogasification of waste. The basic technology relies on anaerobic digestion or fermentation processes. Anaerobic digestion of biomass material proceeds in three different sequential pathways. These pathways are hydrolysis, acetogenesis and methanogenesis. Anaerobic microorganisms perform the first two steps, the hydrolyzer and the acetogen, to break down the biomass molecules of the complex into smaller chains of molecules. Proteins are hydrolyzed into interstitial proteins, peptones and peptides. These compounds are further broken down into ammonia and small chains of fatty acids such as acetic, butyric, propionic and lactic acids. Anaerobic microorganisms that perf...

AI Technical Summary

Problems solved by technology

These proposals still have many shortcomings

For example, adjusting the ammonia concentration in the reactor by adjusting the C / N ratio in the feedstock is a slow process, it is difficult to determine the C / N ratio accurately, and adjusting the C / N ratio proves that in the anaerobic digestion process, when Feedstocks tend not to be adequately manipulated when they tend to produce relatively high ammonia concentrations

Diluting the reactor with water also has many disadvantages

For example, diluting the reactor with water severely reduces the biogas production of the reactor over long periods of time, often resulting in increased dehydration costs

Dilution of existing feedstock increases reactor volume required to digest this feedstock

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