Börger equipment credited for AD functionality

Guy & Wright, a United Kingdom-based tomato producer established in 1928, says it has twice built its own anaerobic digestion (AD) plants to handle its agricultural discards, and it credits Germany-based Börger GmbH for supplying vital equipment.

Guy & Wright built its first digester 15 years ago on its 100-acre site in Hertfordshire, England. Börger says John Jones, great grandson of one of the founders, “could be forgiven for wondering what on Earth he’d taken on.” In addition to producing hundreds of tons of tomatoes each year, he was now “getting to grips with that very steep biogas learning curve of feedstocks, temperatures and digestates.”

Currently, Guy & Wright operates its second, upgraded AD plant, which can handle 7,000 cubic meters (9,155 cubic yards) of material and can create “enough excess power to sell [to] the equivalent of 1,500 homes,” according to Börger.

In 2008, the U.K. company acquired a Börger Multi-crusher to reduce feedstock particles down to 8 millimeters (0.3 inches) in size to enhance the AD process.

John Jones’ son, Rob, who now runs the biogas operation, also saw around that time that tomato leaves were not only extremely difficult to break down, but also low in calorific value.

Thus, the firm now acquires from local sources materials such as citrus fruits, potatoes, grain and cocoa powder—plus processed dissolved air flotation (DAF) sludge from an ice cream manufacturer. That last material provides liquid to help create a “milkshake’ consistency to assist digester performance.

“The Börger Multi-crusher certainly proves itself as a very durable and effective piece of kit for the demands of an AD plant,” Rob Jones says. “We keep one Multi-crusher as a spare so that in any eventuality, we can keep operating – with two always on the go, plus an additional unit now on order. They work very well for us.”

The Multi-crusher chops coarse material to help ensure downstream machines and pumps operate smoothly. The Multi-crusher homogenizes materials at throughput volumes of up to 320 cubic meters per hour (1,400 gallons per hour). In addition to food waste, it can handle fiber materials, pieces of wood, plastics, membranes and textiles in other applications, according to Börger.

A covered lagoon at Guy & Wright produces enough gas to run two of three combined heat and power (CHP) engines and provides retention times of up to six months. This compares with other biogas plants that may only have 30 days of retention, says Guy & Wright.

Guy & Wright bought its second Börger Multi-crusher when it began taking in liquid animal byproducts, for which they also needed a Börger pump.  Using the byproduct (via a new pasteurizer) has enhanced biogas yields by having a feedstock with a high calorific value and also less digestate to deal with, says the tomato grower.

Two biomass boilers are also now in the fleet of machinery, providing additional heat to a plant nursery during winter. Guy & Wright says it has become one of the first companies in the biogas industry to take exhaust gas from a CHP and convert it into CO₂ for its greenhouses. 

Guy & Wright turned to Börger again to address the dwindling capacity of the plant’s open lagoon, purchasing a Börger Bioselect Separator.

In that device, which uses “a purely mechanical process,” according to Börger, liquid is separated from solids in the medium, so nutrient-rich organic matter can go back to the land as fertilizer. 

“We no longer lose capacity in our lagoon,” the Johnson family says.  “This is due totally to the Börger Separator, which protects it; [it] works an absolute treat.”