By Paul O’Callaghan
Whey is a by-product of the cheese manufacturing process. In large industrial dairies, whey presents a waste stream that needs to be managed. Often it is treated as a wastewater and in terms of biochemical oxygen demand (BOD), whey carries a high organic load.
Traditionally, cheese-makers would also keep pigs to produce bacon, with the whey used as a feedstock. In recent years the dairy sector has reinvented whey as a food supplement and created a market for it in the food industry.
According to the American Dairy Products Institute, whey powder and whey proteins represented a global market value of approximately $9.8 billion in 2013. The market value is forecast to reach approximately $11.7 billion in 2017, corresponding to an average annual value growth towards 2017 of 4 percent at constant prices. However, there is still a surplus that exceeds market demand.
Whey contains several valuable components, including lactose, which can be fermented into ethanol. In fact, 1 kg of lactose will produce just over 0.5 kg of ethanol. Surplus whey in the U.S. in 2010 had the potential to generate 203 million gallons of ethanol.
Whey is increasingly seen not as a waste product but as a resource. In 2011, one dairy company in Ireland changed its attitude toward whey, saved money and created revenue streams through sustainable water/energy management and a little creative thinking.
The global dairy industry is estimated to be worth $296 billion. The U.S. alone is estimated to have 485 fluid milk production facilities, 481 cheese production facilities and 196 dry, condensed and evaporated dairy products sites.
The industry uses large amounts of energy and water and is regarded as the single largest source of food processing wastewater in many countries. Every gallon of milk produced requires some 1.5 gallons of water.
The U.S. dairy sector consumes about 80-160 MGD of potable water and creates approximately the same volume of wastewater - equivalent to the volume produced by a city of up to 1.6 million people. However, because dairy wastewater is typically 10 times the strength of municipal wastewater in terms of real loading, it is equivalent to up to 16 million people.
Carbery Milk Products: The Dairy That Did
Carbery Milk Products is a major international food and cheese manufacturer headquartered in Cork, Ireland. The company also has operations in the U.S. and many will be familiar with its flagship product Dubliner Cheese.
Carbery was the first dairy in the world to convert whey to ethanol, which is now used as a feedstock for economic biofuel production. The plant also boasts thermal heat energy recovery, biogas generation, combined heat and power (CHP), phosphorus recycling, water reuse, and uses on-line analysis to reduce product loss. All of this is driven by economics and a desire to increase profit margins.
The process was mirrored at two sites in the U.S., the Golden Cheese Facility in Corona, Calif., operated by Dairy Farmers of America Cooperative, and a plant in Melrose, Minn., operated by Land O’Lakes. The Golden Cheese processing facility has since been decommissioned.
Carbery currently sells 660,000 gallons of bioethanol annually to an oil company for use in its E5 and E85 blends. If you refuel with bioethanol in Ireland, it will have come from this one plant. Ireland is the only ethanol-consuming country in Europe not using sugarcane imported from Brazil.
Recovering Heat Energy
The next step was to recover energy from the 167-198°F (75-92°C) steam in the distillation process and use it to preheat boiler water, clean-in-place system water and in pasteurization processes. The recovered energy reduces the cost of the on-site CHP plant, which runs on natural gas.
The waste stream from the fermentation process is also put to use. An anaerobic digester produces methane, which is burned in an on-site boiler used to pasteurize dairy products and provide hot water.
At around 99°F (37°C), the wastewater itself is quite warm, which is enough to put through a heat exchanger and preheat incoming milk from 40°F (4°C) to 60°F (16°C). This process lowers the temperature of the waste stream, helping meet discharge requirements for the receiving Brandon River.
In addition to calcium, milk contains a lot of phosphorus, a non-renewable resource used in agriculture. Dairies must remove phosphorus before discharging to receiving waters to negate potential environmental impact. Phosphorus also tends to precipitate, blocking pipes and causing process operation issues.
The discharge limit at the Carbery plant is 0.8 mg/L phosphorus so the inflow, which is at 100 mg/L, requires over 99 percent removal. The phosphorus is recovered as a sludge product from the dissolved air flotation process and is applied as fertilizer to agricultural land.
Analysts from BlueTech Research’s parent company, O2 Environmental, encountered the Carbery plant while carrying out market feasibility analysis for the California company APT Water, now owned by McWong Environmental Technologies. APT had an advanced oxidation technology for water reuse - HiPOx - and wished to examine potential applications in the dairy sector. O2 Environmental quantified the number of dairies globally, volumes of water produced, market size and market potential. The analysis looked at which dairies had on-site treatment, what they currently paid for water and what drivers existed for on-site water reuse.
Seeking some treatability tests to generate a cost model for reuse, the O2 Environmental researchers considered Carbery an ideal case study due to the efforts being made at the site toward sustainability and realizing bottom-line value through water and resource optimization.
The drivers for water reuse at the site are:
- Limited volume of water can be abstracted from the river
- All groundwater wells in the areas have been drawn down
- In summer, when river flow is low, very little dilution capacity is available
Results from bench-scale tests showed it would be viable and economical to take effluent that was already high quality, polish it and produce reuse-quality water. It would be cheaper than buying potable water at regular rates.
From the perspective of marginal capital and operating costs, the treatment plant was already in place and was required to meet the discharge permit. The real cost of producing reuse-quality water was the marginal cost of taking it that extra yard in terms of treatment.
O2 Environmental then looked at possible applications for the reused water. The most obvious was boiler feed water, which was produced by demineralization using a reverse osmosis (RO) system.
The reused water could be treated with advanced oxidation before being fed to the RO plant, which would reduce fouling on the RO membrane, increasing the time between clean cycles and prolonging membrane life. It is an application which does not come into contact with food product, reducing concerns about cross-contamination
Wastewater as Lost Product
More recently, Carbery turned its attention to product loss management. When treating dairy wastewater, process engineers will proudly point to 90 percent BOD removal.
The problem in food and beverage wastewater is the waste component. The constituents are almost entirely lost raw materials and product.
In dairy wastewater, 1 kg BOD is equivalent to 9.3 liters of full-fat milk. By converting BOD loading back to a milk-equivalent and then applying a nominal price of say 30 cents per liter of milk, it is possible to show the cost of the product - and that does not include the wasted thermal energy and other costs that went into processing it. On average, globally, 3 percent of product is lost in the dairy industry, a consistent rate across the sector.
Carbery installed a number of BioTector online total organic carbon (TOC) detectors from Irish instrumentation company BioTector Analytical Systems at key drains around the plant. These machines are particularly robust analyzers based on chemical oxidation of carbon and measurement of CO2 in the off-gas. However, an analyzer on its own will do nothing - the data must be acted upon. So the requirement is for an analyzer, a management system and data dissemination to operators.
Product loss management requires a relatively low capital investment, and a 15 percent reduction in lost product is usually very achievable. Payback is quite dramatic - typically less than a year - and savings are significant, reaching over $1 million at the larger dairies.
Carbery achieved a 30 percent reduction in lost product and saved $1.7 million every year, plus other savings. The company was able to boost production by 8 percent one year, without increasing the footprint of the treatment plant, which saw a 30 percent reduction in loading.
While the savings are only calculated on the value of the product saved and the decrease in wastewater treatment costs, energy is also saved as lost product is no longer pasteurized. The further down the process chain product losses occur, the higher the value of embedded process costs wasted.
The greatest challenge in this resource recovery approach to dairy process is measurement. Dairies present a challenging environment for analyzers - the industry cannot tolerate equipment that does not work.
Unless the measurement itself is absolutely credible and accurate, it is extremely difficult for management to begin to set targets for key performance indicators. To be successful, implementation requires a complete management approach.
O2 Environmental’s research shows that when water industry professionals really get close to their clients’ processes, there are many ways and opportunities to deliver real value to the bottom line and identify opportunities for water innovation with a compelling return on investment. Where innovation delivers its own value, it creates its own market.
Editor’s Note: These themes will be explored with corporate water industry leaders, including Coca Cola’s Dr. Paul Bowen and L’Oreal’s Hans Bucholz, at the BlueTech Forum, June 1, 2016, in San Francisco, Calif. O2 TAG and BlueTech analysts will provide briefings on how innovation can deliver value for corporate water users. For more information, visit www.bluetechforum.com.
About the Author: Paul O’Callaghan is CEO of BlueTech Research, a consultancy that provides water technology market expertise and strategic advice on technology development and commercialization to start-up firms, the investment community and larger water corporations.