Environmental Energy & Engineering - Technologies

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CONVENTIONAL DIGESTION (1 of 9)

CONVENTIONAL DIGESTION

Completely mixed digesters normally process slurries having a solids content of 4 to 8% whereas plug flow anaerobic reactors are used to digest slurries having a solids content of 8 to 14%. The methane content of the gas produced is dictated by the chemical composition of the waste. Conventional digestion requires large tanks since the Solids Retention Time (SRT) is equal to the Hydraulic Retention Time (HRT). It is the solids retention time (SRT) that determines the percent of the influent solids that are converted to gas and thus the gas yield.

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HIGH RATE ANAEROBIC DIGESTION (2 of 9)

HIGH RATE ANAEROBIC DIGESTION

High rate anaerobic digestion retains anaerobic bacteria through a variety of means. The process decouples the hydraulic retention time (HRT) from the solids retention time (SRT). The high rate anaerobic “contact process”, utilizing gravity sedimentation, has been used for over a hundred years. However gravity sedimentation produces a low concentration bacterial recycle stream. The process can be significantly improved (SRT / HRT ratio) by producing a concentrated recycle stream without adversely affecting the anaerobic bacterial consortia.

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MAXIMUM SOLIDS CONVERSION TO GAS (3 of 9)

MAXIMUM SOLIDS CONVERSION TO GAS

Maximum conversion of volatile solids to gas is achieved with the stabilization process. The stabilization process can achieve the highest SRT / HRT ratios and consequently the largest reductions in anaerobic reactor size. The process is ideal for waste streams such as swine waste or flush dairy waste that contain rapidly degrading constituents and slowly degrading particulate matter.

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BIOMETHANE GAS PRODUCTION (4 of 9)

BIOMETHANE GAS PRODUCTION

Over 70% of the energy value in a biogas is lost when converting biogas to electrical power. As a result, biomethane has three times the value of electricity selling for $100 per megawatt hour when sold as a renewable transportation fuel,. However current processes used to convert biogas to clean methane gas (biomethane), such as water scrubbing or pressure swing absorption (PSA) are expensive and do not justify cleaning biogas to produce renewable methane gas.

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PASTEURIZATION PROCESS (5 of 9)

PASTEURIZATION PROCESS

In many cases it is desirable to produce a pathogen free soil conditioner or fertilizer that can be sold to the public or utilized on food crops. E3's pasteurization process is the most economical solution to producing a “Class A” pasteurized product. Energy requirements and pasteurization reactor size are significantly reduced since less than 20% of the influent waste is processed through the pasteurization unit. It is the most economical method of producing a "Class A" product.

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NUTRIENT RECOVERY PROCESS (6 of 9)

NUTRIENT RECOVERY PROCESS

The anaerobic digestion process does not remove any of the nutrients (N P and K). It simply alters the form of the nutrients from particulate to soluble and gaseous products. A majority of the nitrogen is discharged from the digester as ammonium. A majority of the phosphorus discharge from the digester is associated with a fine particulate matter. Coarse liquid / solids separation (screw press, slope screen) does not capture a majority of the phosphorus or nitrogen.

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HIGH SOLIDS DIGESTION (7 of 9)

HIGH SOLIDS DIGESTION

In many cases it is desirable to replace the energy consuming, greenhouse gas emitting, “composting” process with anaerobic digestion that produces energy while minimizing greenhouse gas emissions. E3's high solids, zero emission process can be utilized to digest solid substrates such as poultry manure, yard waste, crop residues, and the food fraction of municipal solid waste.

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AMMONIA NITROGEN RECOVERY (8 of 9)

AMMONIA NITROGEN RECOVERY

If anaerobic digestion is used to process waste containing protein or other nitrogenous compounds ammonia will be produced and discharged in the effluent slurry. After separation, a majority of the ammonia nitrogen will be discharged with the effluent liquid. Upon discharge a portion of the ammonia nitrogen will volatize as a uncontrolled emission that may form fine particulate matter (PM 2.5), or undergo nitrification / denitrification producing nitrous oxide, a powerful greenhouse gas. The ammonia nitrogen that remains in solution may adversely inpact surface and groundwater.

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ZERO EMISSION LIQUID / SOLID SEPARATION (9 of 9)

ZERO EMISSION LIQUID / SOLID SEPARATION

E3 has developed a unique zero emission, totally enclosed, confined atmosphere, liquid solids separator for the separation and recycle of anaerobic solids and bacteria. The separator can be used for a wide variety of purposes since the influent gases are confined and separated from the atmosphere (See www.cyclus.com for animation).

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