Case Study: Converting waste into bioenergy

Posted By GWE / June 11, 2014 / Related technologies: RAPTOR®,

Global food processor Remo-Frit utilizes an innovative waste treatment system that turns effluent and solid residues from its operations into biogas, which is then converted to electricity.

The high value of industrial wastewater

Remo-Frit specializes in the production of fresh chilled potato products, manufacturing French fries and potato specialties for export to markets in Europe, America, Africa, the Asia-Pacific and elsewhere. Remo-Frit has demonstrated the environmental and economic benefits of converting waste products into green energy, transforming a potential problem into a sustainable solution offering greater profitability.

The manufacturer enlisted the services of Global Water Engineering Ltd (GWE) build a complete wastewater treatment plant and a RAPTOR™ plant for the solid residues of the Remo-Frit potato processing plant in Verrebroek, Belgium.

This is in keeping with Europe’s food and beverage producers who are highly focused on minimizing waste and making the most of by-products in re-use, recycling, and recovery.

At the heart of this state-of-the-art wastewater, treatment operation is the Remo-Frit RAPTOR system. Inaugurated this year, the system converts nearly all of the potentially environmentally harmful organic content of the solid wastes into green electricity and valuable fertilizer products. What’s more, the RAPTOR process is complemented by (and integrated with) a high-efficiency GWE wastewater treatment plant to achieve the very high wastewater quality standards and the optimum biogas production efficiencies specified by Remo-Frit.

How does RAPTOR™ work?

The RAPTOR™ process (or RAapid Transformation of Organic Residues) is a powerful anaerobic digestion process which, in this application, consists of a mechanical pretreatment of the organic residues (mainly the potato peels), thermophilic hydrolysis in a TAR (Thermophilic Acidogenic Reactor) followed by methane fermentation in a thermophilic digester of the ANAMIX™ – T type.

Out of a 3,300 m3 digester for the potato peels and primary sludge, GWE is able to produce up to 14,150 m3 of biogas per day from 230 Ton of organic residues per day (potato peels + primary sludge).

On top of that, the anaerobic wastewater treatment plant produces another 3,350 m3 of biogas per day.

Together, this amount of biogas is equivalent to 8,410 kg or 9,834 l of light fuel oil per day, or 3,106 tons of fossil fuel a year, worth nearly €3 million or around $US4 million.

Along with electricity production from biogas produced from wastewater and solid residue, steam is produced from the hot exhaust gases from the biogas engine. The steam is then used for cooking higher grade organic residues intended for animal feed. Meanwhile, the cooling water of the engine is used to maintain thermophilic conditions throughout the RAPTOR process and mesophilic conditions in the UASB (ANUBIX – B).

Wastewater treatment process

The ca. 3,500 m3 per week of wastewater generated by the factory (5,000 m3a week at full capacity) is treated in a new primary clarifier, with the primary sludge sent to the RAPTOR plant, followed by an existing Upflow Anaerobic Sludge Blanket (UASB) type of anaerobic reactor of 2,045 m3, and further processed in a new nitrification/denitrification plant. The wastewater then passes to a new tertiary treatment with coagulation/flocculation and dissolved air flotation (DAF) treatment.

According to Remo-Frit, this newly upgraded and expanded wastewater treatment system attains 99.5% chemical oxygen demand (COD) reduction, from 22,300 mg COD/l down to a very low 50/60 COD/l.

Furthermore, nitrogen and phosphorous levels of less than 10 and 3 mg/l respectively are obtained.

Biogas produced from Remo-Frit’s waste streams undergoes sulfur removal (or ‘sweetening’) for environmental and plant reliability purposes, using GWE’s BIO-SULFURIX™ process, followed by drying in GWE’s GASODRIX™ system.

How does biogas processing work?

A set of blowers feeds the gas to the electric power generators – an environmentally friendly incineration type ground flare is installed for emergency purposes.

A biogas engine (CHP) of 1,200 kW was installed in a first stage of the project (the second one of about 500 kW is being ordered to be able to cope with increasing biogas production due to factory expansion.)

The wastewater treatment plant sized for 1,000 m3/day is treating the factory’s wastewaters and the digestate of the RAPTOR™ process. It consists of a primary clarifier, a UASB type of anaerobic reactor (ANUBIX™ -B), a pre- and post denitrification, nitrification and post aeration, a clarifier and a final DAF for phosphorous removal with iron chloride. Finally, the effluent is discharged in a river.

“Remo-Frit is setting world green energy and water purity benchmarks for food processing by harnessing both of its organic waste streams, in wastewater and organic solids,” said Mr. Jean-Pierre Ombregt, GWE chairman and CEO.

“This is a lead that can be followed by food and beverage processing companies globally, wherever they produce an organic waste stream.”

Bottom line impact

Energy savings produced by biogas production are achieved in perpetuity, with fossil fuel equivalent savings totaling $US40 million (nearly €30 million) in the first decade at today’s prices, according to GWE.

Savings quickly repay the cost of the plant – typically inside two years – while achieving permanent environmental benefits by replacing fossil fuel.

According to GWE, food processors such as Remo-Frit – including breweries, fruit, food waste, agro-industries, and energy crops including corn – can easily use this technology to generate energy for use in powering factory plant such as boilers or to feed electricity generation sets to produce electricity for the production plant or for feeding back to the local grid.

“By harnessing both of its organic waste streams – contained in wastewater and organic solids – Remo-Frit is setting world green energy and water purity benchmarks for food processing,” says Pascal Pipyn, executive vice president, process and research and development for GWE.