Green energy from wastewater treatment unlocks profit potential for the dairy industry
Despite surging energy prices and ever-spreading carbon taxes to counter global warming, many sections of the dairy industry are still pouring potential profit down the drain by overlooking the green energy potential of waste water. The industry has tended to treat its wastewater as a cost, and as an area where production process mistakes can be flushed. "If there were spills or if a production product was out of specification, it would be flushed down the drain. That's where the mistakes go," said wastewater and green energy specialist Mike Bambridge, Managing Director of CST Wastewater Solutions. "Such outdated approaches have resulted in bigger and bigger lagoons that are both ground water hazards and big consumers of expensive energy and fossil fuel because of the large energy-intensive aeration systems needed to treat their contents. They also create a lot of sludge and disposal problems."
Bambridge believes that there lies a huge, often hidden potential in using wastewater as a source of renewable energy rather than seeing it as a cost. His company, which has 20 plus years of experience in this regard in Australasia, represents Global Water Engineering (GWE), which has to its credit more than 250 plants producing biogas as part of the industrial effluent clean-up system, of which more than 75 were supplied with subsequent biogas utilisation systems for clients worldwide.
Users of GWE technologies extend from the new $A120 million Bluetongue Brewery in Australia to global concerns such as Budweiser, Chang, Carlsberg, Coca Cola, Corn Products Int'l., Danone, Fosters, Heineken, Interbrew, Kraft, National Starch & Chemicals, Nestlé, Pepsi Cola, SAB-Miller, San Miguel, Singha, Sunkist and Tsingtao, Cadbury Schweppes.
Many of the latest installations use advanced technologies - including anaerobic pre-treatment of water and aerobic polishing - to enhance water discharge purities while converting waste to methane to be burned to power boiler and hot water systems, for example, or to power generators and permanently replace fossil fuels. On average, the removal efficiency of GWE's anaerobic wastewater treatment installations is as high as 90-95%, easily bringing the organic load down to regulatory discharge standards for most types of wastewater.
GWE CEO Jean Pierre Ombregt said the concept of using wastewater to create green energy is much more widely applicable than often realised. He continued, "Any factory with a biological waste stream or wastewater with high COD (Chemical Oxygen Demand) can easily use this model to generate energy - particularly the dairy industry, for which GWE technologies such as its Flotamet system combined with its proprietary Dissolved Biogas Flotator (DBF) are specifically designed to take the high levels of fats and oils prevalent in dairy factory effluents."
So far, most industries have mainly been focusing on treating their effluent to meet local discharge standards. By doing so, wastewater treatment installations have only generated additional costs and have never been seen as revenue generators.
"Instead of looking at efficiency, and getting the inputs and outputs optimised, the dairy industry has traditionally employed big systems to cover process mistakes, with big lagoons and the like requiring huge amounts of energy to aerate, said Bambridge. "However, applying anaerobic wastewater treatment sheds a whole different light on the cost structure of wastewater treatment infrastructure. It can now actually become a substantial additional source of income for many processing plants."
Dairy wastewater is well suited for anaerobic treatment, followed by an aerobic polishing treatment if required. GWE has several anaerobic systems, some of which can be applied on dairy wastewater.
There is no such thing as a standard dairy factory, and a standard dairy wastewater treatment. There are different types of dairy factories with different products (milk packaging, milk powder, cream, butter, yogurt, ice cream, cottage cheese, soft cheese, hard cheese, fruit based products, custard, etc) all with very different wastewaters, and also different levels of product recovery (example, whey and/or whey proteins). In the end, the type of production determines the wastewater characteristics.
The COD of dairy wastewater can be anything between 2,000 and 10,000 mg/l, for cheese factories also much more (50,000 mg/l, in case of no whey recovery).
The amount and type of Fat, Oil & Grease (FOG) is also important. In case of ice cream and butter, there is a lot of FOG in the wastewater, but it can be easily removed by DAF (Dissolved Air Flotation), so that a high rate ANUBIX-B system, sensitive to excess FOG in the wastewater, is possible and often preferred. In other cases, with a lot of milk processing (incl. milk powder), the FOG in the wastewater is basically diluted milk, and the FOG (fat) is very much emulsified, so that a DAF cannot always remove it properly, even after chemical treatment. In that case, GWE offers two anaerobic systems which can treat dairy wastewater without or with limited FOG removal: the ANUBIX-C system and the FLOTAMET system.
GWE claims that these systems are often the best choice if the FOG removing pre-treatment (by DAF, with chemicals) results in problematic and expensive sludge disposal. The cost depends much on local possibilities for sludge disposal. Both the ANUBIX-C and especially the FLOTAMET system can effectively degrade moderate amounts of dairy fat, thereby avoiding big DAF sludge disposal problems. The FLOTAMET system degrades FOG best but requires a high operating temperature, in case of a high FOG/COD ratio.
Generating power from wastewater
Wastewaters from the dairy industry are typically highly loaded with organic pollutants that can be treated advantageously by means of anaerobic processes. Closed anaerobic reactors generate large quantities of methane (CH4) from the organic materials in the wastewater that can diminish or even completely replace the use of fossil fuels in the production process. To bring some perspective to the value, one tonne of COD (chemical oxygen demand) digested anaerobically can result in 350Nm3 of methane, equivalent to 0.15MW of power.
For specific industry applications with high organic loads, enough biogas can be generated to fully cover a factory's energy needs and still have a biogas surplus to feed it into generators and sell electricity to the national grid, often generating carbon credits, where these apply, as well as profit.
For a greener footprint
The GWE closed anaerobic process systems prevent large quantities of CH4 being emitted into the atmosphere. With CH4 being 21 times more harmful than CO2, GWE's anaerobic wastewater solutions can also qualify for Emission Reduction Certificates for projects in countries listed under the United Nations Kyoto Clean Development Mechanism (CDM) and Joint Implementation (JI) programs.
Besides the economical advantage of efficient anaerobic wastewater treatment, there is clearly also the environmental advantage, significantly reducing factories' carbon footprint. Not only by supplying renewable energy and thus reducing or even eliminating the use of fossil fuels, but also by replacing more traditional, CH4-polluting, open lagoons and by replacing power consuming and sludge producing traditional aerobic WWTPs.
Is 'green' power viable?
The main criterion for energy-generating projects to become viable is the COD loading rate. The higher the organic load of the wastewater, the more biogas and thus renewable energy can be generated from it. Cost of fuel also plays a significant role. As the world is learning to live with higher energy prices, choosing anaerobic technology now holds the key to immediate and future safeguarding of power supply for many industries.
In selecting a suitable technology provider for wastewater treatment with biogas utilisation, it is crucial to partner up with a reliable, experienced team. From the design to implementation stage and beyond, into operations and maintenance of the plants, it is very important to look at the feasibility of a biogas project, both technically and economically. It is extremely important to choose the right reactor configuration. Each industry has specific wastewater characteristics, requiring thorough analysis and subsequent careful selection of the most suitable reactor design for these characteristics.
"Too often we have seen companies left disillusioned after trying to implement anaerobic wastewater treatment with biogas reuse in the past. Although anaerobic technologies have improved significantly in recent years, the world is still littered with too many examples of how it is NOT supposed to be done," says Ombregt.
GWE and CST say environmental initiatives such as green energy generations from wastewater treatment do not always get as much attention as the more traditional renewables, such as solar and wind. But in fact there is a huge, often hidden, potential in using wastewater as a source of renewable energy. The GWE/CST Wastewater Technology partnership encourages businesses with organic content in their wastewater and waste streams to investigate the anaerobic potential for their specific case.
© H2O 2011
