A food processing company is in the business of selling food. A drinks company makes beverages. A paper company produces paper. But all of these companies have something in common – they also produce waste streams, and they have to deal with wastewater treatment as part of their business. They all aim to manage their waste as cost-efficiently as possible while ensuring clean water is discharged into the environment.
Nowadays a new view of waste is emerging in industry – waste as a resource, not just a cost. Novozymes Biologicals is helping to bring about this change in perception with an innovative new product called BG Max launched in March 2010, initially to the food and beverage industries.
“The focus before has been on removing compounds from wastewater. Now a wastewater facility can generate value through the production of biogas, and BG Max can help maximize that value,” says Chris Day, Global Marketing Manager for wastewater solutions at Novozymes Biologicals.
Faster payback time
BG Max is the first biological product of its kind designed to enhance the production of biogas in wastewater treatment. It is a combination of beneficial microorganisms and fast-acting enzymes chosen for their ability to generate biogas and increase the efficiency of anaerobic treatment.
BG Max can be used in a variety of food and beverage industries that use anaerobic treatment for high-strength wastewater streams. “High strength” means that the waste has a high chemical oxygen demand (COD) – a measure of the amount of degradable organic compounds in water and a useful indicator of water quality. “Anaerobic” means a biological system that works without the presence of air. Such systems are often used to treat waste before further treatment in an aerobic system (see Fig. 1).
Anaerobic systems produce up to five times less solids than conventional aerobic activated sludge systems and require less energy. One high-tech solution is known as an Upflow Anaerobic Sludge Blanket (UASB) where biogas is collected from the closed unit. With BG Max, investments in systems like these will now pay back quicker due to increased biogas production.
From waste to methane
Biogas is generated during a four-step biological process. Hydrolysis, the first step of the process,results in the conversion of carbohydrates, fats, and proteins into sugars, fatty acids, and amino acids. Following hydrolysis, the acidogenesis step results in the production of carbon acids. The third step, acetogenesis, results in acetic acid, carbon dioxide, and hydrogen. The final step,methanogenesis, is when methane is formed by specific microorganisms called methanogens.
BG Max is most active during the hydrolysis and acidogenesis steps. The microorganisms and enzymes in BG Max degrade a wide range of organic compounds including proteins, fats, sugars, and starches.
Maximum value
BG Max is designed to maximize the performance of a variety of anaerobic treatment units from UASBs to covered lagoons. But even when the biogas is not collected or reused and merely burned off, it can still make sense to use BG Max because it can improve the efficiency of anaerobic systems and provide cost savings.
Apart from an increase in the amount of biogas generated, one of the primary benefits of using BG Max is a decrease in the COD load. Any additional COD load removed by BG Max in the anaerobic system reduces overall solids handling costs and overall energy consumption. Figure 2 shows the COD reduction at a fruit preserve processing plant. After adding BG Max, the COD removal efficiency increased by 18% in the anaerobic treatment unit. This stabilized the downstream aerobic system and reduced solids handling costs and energy demand.
More biogas
Figure 3 shows the results when BG Max was added directly to an anaerobic unit at a US swine processing company in October 2009. The yield of biogas per kg of COD removed had more than doubled by December.
At another US swine slaughterhouse that processes 300–400 head of swine per day, a variety of organic-rich wastes are treated. They are fed into an anaerobic digester to reduce solids and generate biogas used to heat the facility. The facility’s operators had been forced to underload the digester due to poor performance during high-loading operations. They contacted Novozymes for a solution that would help stabilize the digester and improve reactor efficiency.
Novozymes’ answer was BG Max, which was added to the inlet of the anaerobic tank. One month later the customer generated an additional 538 m3 (19,000 ft3) of biogas per day, a 29% increase. As a result of the greater biogas production, the rate of electrical power generation by the combined heat and power plant increased by 51% (an additional 1,800 kWh/day). Not only did the volume of biogas increase, but the efficiency of the operation improved to such a degree that the plant managers could maximize the load to the digester.
Rising popularity
Anaerobic wastewater treatment systems are made to handle high organic loads. In comparison with aerobic systems, they generate less waste sludge, have lower operating costs, use less energy, and have the benefit of generating biogas. They also contribute to a reduced carbon footprint, and the generation of biogas can qualify for carbon credits, which can be sold on the market. Therefore adopting an anaerobic system that recovers biogas is a way of meeting corporate sustainability targets.
“We continue to see growth in the market for anaerobic systems as customers look for ways to improve the profitability and environmental footprint of their facilities,” comments Chris Day of Novozymes Biologicals. “As these systems become more efficient through the use of BG Max, and also more visible in the market place, their popularity will only increase.”