Meeting heat and power loads down under – Australian meat processing plants are a fine match for cogeneration

Food processing plants are often suitable sites for cogeneration. Here, Tracey Colley outlines the case for cogeneration at meat processing plants in Australia, where refrigeration and hot water loads are considerable, before looking at how obstacles to cogeneration in Australia may be overcome.

Meat processing accounts for 20% of the Australian food and beverage industry economic value in terms of sales turnover, and 30% of the employment. Beef and veal contribute over 50% of the total meat production as measured by product weight. Although the amount of export for all meat products, including poultry and pig meat, is about 34%, about half of all beef, veal and mutton production is exported to regions such as Asia, the Middle East, Europe and North America.

Beef and veal accounts for 50% of Australia’s meat production
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Processing plants range in size from those processing 200 livestock per week to large plants processing more than 4000 livestock per day.

Typical plant energy use

The amount of energy used in plants varies depending on their size and on-site operations. Industry key performance indicators were developed (by Meat and Livestock Australia Ltd) in the 1990s for energy use. The latest figures are 3389 MJ per tHSCW, with electricity accounting for about one third of the consumption; steam about 50% and hot water the remainder.

Thermal energy use

Steam tends to be of relatively low pressure, only up to about 1000 kPa. Rendering plants process material from the kill floor and boning rooms, so continue operation for a number of hours after production in the main process areas has ceased, allowing heat to be recovered for cleaning of the main process areas.

Waste heat is recovered from the rendering plant to produce hot (85à‚°C) and warm (45à‚°C) water for use mostly in the meat processing plant. Supplementary fuel may be used to achieve the required energy input. Efficient use of steam and the maximization of heat recovery from the rendering plant are key to minimizing overall plant energy consumption. Co-location of rendering plants with meat processing plants improves the energy efficiency of both plants due to the opportunities for heat recovery and heat integration. Ideally, an integrated plant would aim for minimizing the hot and warm water use in the meat processing plant so that the rendering plant can meet the total heat requirement for that process without supplementary fuel.

Hot water is mostly used for knife and equipment sterilization and a slightly lesser amount is used for plant cleaning. Thorough cleaning is required after operations cease to ensure that stringent hygiene and food safety requirements can be met à‚— this can take a number of hours. Warm water is used for cleaning and for personnel hygiene requirements, such as hand-wash stations, boot-wash stations, apron washing and, to a lesser extent, amenities such as showers. Personnel hygiene requirements occur during or immediately after production, while cleaning use can extend for hours after production has ceased. Once cleaning has been completed, the hot and warm water requirements drop back to basically nothing.

Electrical energy use

The refrigeration system uses the vast majority of the electricity consumed on site, generally 60%à‚—70% of the total, possibly more in hot, humid weather. Motors are a distant second in terms of overall consumption, accounting for about 20% of total site electricity consumption. The remainder is air compression and lighting. At the start of a shift, initially the peak load is created by equipment items being turned on in the process areas. Most process areas tend to start operation at the same time, with minimal time lags between areas, which can mean that peaks also occur after break periods for workers.

The refrigeration load is dominated by the chillers that receive carcasses from the kill floor. Livestock enter the kill floor at about 38à‚°C and the carcass surface temperature must be reduced to 7à‚°C as quickly as possible to prevent the growth of Salmonella and E. coli bacteria on the surface, which is an important food safety requirement.

The peak usage in the refrigeration system depends on the operating hours of the plant, but tends to coincide with highest ambient temperatures on warm summer afternoons. This consumption extends beyond the operating time of the kill floor and boning rooms, as the carcasses can take a number of hours to reach the required temperature of 16à‚°C. Failure to meet the required product target temperatures within specified time periods can mean that product cannot be used for human consumption, and so is avoided at all costs. This means that plants generally have some redundancy in their refrigeration plant, although, interestingly, a site may not have backup power supply to cover chiller requirements in the event of grid electricity supply failure.

The electricity and thermal energy requirements for meat processing plants occur at the same time and during peak tariff periods for the electricity supply system.

Ideal candidates for cogeneration

Meat processing plants, like many food processing sites, can be ideal candidates for cogeneration. The daily variation in load means that the electricity load factor tends to be fairly low, often around 60%. This can mean that a site ends up being penalized financially through the demand portion of its tariff, particularly as the site peak requirement tends to coincide with the electricity supply system peak. A cogeneration plant which operates as a peak shaving/lopping plant can assist in improving the overall electricity load profile, and increasing the cogeneration plant fuel use (normally gas) at times when it is typically non-peak for that system.

The coincidence of the site peak electricity demand with the electricity supply system peak can lead to higher electricity transmission and distribution losses, which lowers the overall efficiency of supply of the larger grid.

Most meat processing plants have a peak electrical load of less than 5 MW, which means that plants are ideally suited to reciprocating engine cogeneration units. The required process temperatures mean that a higher percentage of the waste heat from the reciprocating engine can be recovered, including the jacket water and possibly even the lube oil cooling system, both of which have temperatures of 50à‚°Cà‚—70à‚°C. When these factors are combined, it means that the overall efficiency of a meat processing cogeneration plant can be at the higher end of the spectrum at 80%-plus. The nature of the power-to-heat balance at meat processing sites means that sites can generally operate cogeneration plants without exporting electricity to the grid, which can simplify both the business case and the electrical connection requirements for the plant.

Most meat processing plants have a peak electrical load of less than 5 MW, which means that a cogeneration plant will generally not require any additional gas supply infrastructure as the current gas supply pipeline will generally be adequate to supply the extra tranche of gas for the cogeneration plant. This may avoid the need to duplicate the line into the plant, which would add to the capital cost of the project.

Barriers and obstacles to cogeneration

If cogeneration is such a great technical fit, why aren’t there more plants with cogeneration? Perhaps the most significant roadblock for cogeneration in the meat industry is the most usual one for smaller-scale cogeneration à‚— for the host site, power generation isn’t its core business, and yet it is important enough that it does not want an external party owning or controlling it either. There is substantial potential for an external entity, such as an energy services company, energy retailer or equipment supplier, to develop a blueprint for a meat industry cogeneration project. This would enable the knowledge gained from one project to be translated into improved outcomes for subsequent projects, and the administration and legal costs to be spread over a number of projects.

Many meat processing plants are often located in regional areas near the stock that supply their plants, rather than near major urban centres. This can mean that skilled external resources for the maintenance and operational support of cogeneration plants are not as readily available. When electricity and heat supply is so critical to the operation of the plant, it is understandable that host sites are wary of committing to technologies which may not be adequately supported in their local area. Plants cannot afford to wait for hours for their plant to be restarted à‚— if the power stops, so does production.

One way of overcoming this would be to develop a cluster of cogeneration plants in a region, preferably with the support of government agencies responsible for regional development. A critical mass of cogeneration plants could lead to a strengthening of the on-site or local skills base for this technology.

As investment in a cogeneration plant would generally not increase market share or site throughput, it is often required to be more economic than projects which do have those attributes. Unfortunately for cogeneration projects, the economics often require a payback of five or more years, as well as a larger sum of capital compared to a straight boiler project.

On the economic front, like many other small-scale cogeneration plants, meat processing cogeneration plants can provide electricity network support benefits and other locational benefits. It is not always possible for the developer to capture these economic benefits, as they are often split between various parties in the electricity supply network, such as the distribution system network providers and electricity retailers.

Information about the value of these benefits may not be readily available to the host site, such as the costs to the electricity network owner of network augmentation. This can mean that potential host sites lack the information to make transparent decisions and negotiate on an equal footing with other parties who may benefit from them installing a cogeneration plant. This highlights the need for the active involvement and disproportionate amount of market power of players in the current electricity supply arrangements for the potential host site when compared with the host site owner. This can mean that projects fall into the ‘too hard’ basket for host sites when compared with the simpler and trusted ‘replace like with like’ option.

Any new project which requires divergence from current practices requires the host site to be comfortable with the additional perceived level of risk it is taking on. The benefits, such as cost saving, backup power supply or increased reliability of supply, need to stack up against these perceived risks for a site to be comfortable with progressing the development. This highlights the importance of non-economical or technical factors in project development, such as a strong, co-operative working relationship between the host site and the project developer (if they are separate entities).

Changing responses to a changing world

There are a number of changes currently occurring in utility supply which tend to favour on-site cogeneration for food processing sites such as meat processing plants. The foremost of these is that many plants do not have backup electricity supplies, but instead rely wholly on grid-supplied electricity. Climate change projections indicate that in future, storms and severe weather events will be more frequent, with the potential to increase the interruptions to grid electricity supply and therefore decrease the reliability of the power grid.

Peak site electricity consumption is generally created by peak summer cooling demand due to higher ambient temperatures and humidity. Once again, climate change is likely to increase the duration and frequency of high-temperature events and may also lead to an increase in relative humidity, with consequent increases in refrigeration load. If the electricity supply system peak is also a summer peak, due in part to the large growth in residential air conditioning loads, then the combined effect may require electricity network augmentation. This provides an ideal opportunity for embedded generation, such as on-site cogeneration, to reduce the system peaks by removing load from the system on a $/kVA basis.

As meat processing plants use quite a lot of water in their process, there is potential to treat and recycle this water for cooling use in the cogeneration plant. Large-scale centralized power generation plants which are not located near a major body of water, such as coal-fired power plants in Australia, are coming under increasing pressure due to the amount of water they consume which ends up as water vapour. Often, the water used is of drinking quality and is in competition with other consumers, such as agriculture and residential users.

A related issue is the decreasing tolerance of the general public for odour emissions from sites. Meat processing facilities used to be away from residential areas, but new housing developments are increasingly encroaching on ‘industrial’ land, putting pressure on sites to do something about their odour emissions.

Many meat processing sites with adequate space available treat their wastewater through an extended pond treatment system. The system starts with water entering an anaerobic pond after primary treatment for solids and oil/grease removal, through a facultative pond to aerobic polishing ponds. The anaerobic ponds can generate methane as a result of the anaerobic degradation of the organic material in the wastewater. Unfortunately, the organic material generally includes naturally occurring sulphur, and the process which leads to the favourable production of methane can also lead to the emission of reduced organic sulphur compounds, which are detectable at relatively low levels and generally considered objectionable.

The simplest model for removing this odour source is to cap the ponds and flare the resultant gaseous emissions, but if the anaerobic wastewater treatment pond and the plant are sufficiently close together, there is potential for the biogas to be used in the plant. The biogas can be captured, treated to remove corrosive compounds and used to offset either boiler or cogeneration plant fuel consumption. The on-site utilization of biogas can assist with recovering some of the costs of covering the ponds.

Capitalizing on the potential

Cogeneration projects require forward planning, as the lead time for sourcing a reciprocating engine or gas turbine can be well in excess of 12 months, meaning that project planning can be on a much longer timeline than a simple boiler replacement project. This means that sites need to take a longer-term approach to planning their utility requirements.

The trend in meat processing plants is for integrated supply chains, whereby feedlots supply meat processing plants with stock, and plants carry out more value adding on site. This increases the bioenergy resource available at a meat processing plant as it may have access to manure from feedlots as well as its own wastewater and waste organic material from the process. Waste organic material from the process can include paunch material, wastewater solids from the pre-treatment upstream of the anaerobic pond and manure from the stockyards.

Many of these wastes are organic and therefore highly recyclable, particularly in terms of recycling nutrient and organic matter back to the food chain to reduce the amount of inorganic nutrients and fertilizers required. Treatment of these bioenergy resources means that the carbon content can be recycled as energy, and the nutrients pass through the conversion process and come out the other side as a stabilized waste. This is generally looked on favourably by both environmental regulatory agencies and health regulatory agencies.

Health regulatory authorities may be concerned about the disposal of meat processing wastes due to the potential for pathogen transmission to the general population, such as Q fever. Treating the wastes at elevated temperatures assists with pathogen destruction. Some plants have already installed bioreactor or biodigester systems for treating all the wastes from the plant, although the higher capital costs of these systems when compared with traditional wastewater pond treatment systems means that generally there have to be other factors involved. The factors can range from the availability of government funding grants to the location of the meat processing plant where there is not land available for a pond treatment system.

The trend towards more-intensive livestock production, with the resultant concentration of waste generation into a smaller area, increases the availability of bioenergy feedstock and the need to manage the waste appropriately to prevent adverse environmental impacts, such as eutrification of waterways. Biodigesters provide an elegant solution to this problem, particularly as they have a much smaller footprint than pond systems and can operate year-round in climates where low winter temperatures would adversely affect anaerobic pond operations.

Carbon trading schemes, which put an economic value on reducing carbon dioxide equivalent emissions, can add substantially to the economics of biogas projects, given that methane has 23 times the power of carbon dioxide to warm the atmosphere. Biogas projects can provide a large lump sum of abatement in one project, particularly if the biogas is used to offset grid electricity consumption and lead to a lower overall carbon intensity of energy supply at a meat processing plant.

In Australia, cogeneration has generally only been marginally economic for small plants due to the price differential between natural gas and electricity. Electricity prices are projected to rise in the order of 30% in the short term, and in some areas, natural gas prices have fallen due to the availability of cheaper coal-seam methane. Consequently, the economics of cogeneration have shifted in favour of more projects even before other benefits, such as electricity network support payments, are considered.

The next five to 10 years should see a growth in cogeneration and bioenergy projects in the meat processing sector if the roadblocks of split economic incentives and longer project timelines can be overcome.

Tracey Colley is with Sustaining Australia, Stockton, New South Wales, Australia.

Typical meat processing plant

Meat processing plants generally have three major sections: the kill floor, boning room and rendering plant. On the kill floor, livestock are processed to remove the hide, hoofs, blood, head and internal organs, leaving the hot carcass, which is then put into chillers. This is a key production measuring stage, where the weight of product leaving the kill floor is measured as tonnes of hot standard carcass weight (tHSCW). The boning room processes the carcasses depending on customer requirements, ranging from half carcasses to retail-ready packaged products. About half of the live weight ends up as hot carcass, and about 70% of the hot carcass ends up as final product leaving the boning room.

The rendering plant takes the off-cuts of fat, meat and bone from the kill floor and boning room and converts it into meal (blood and meat) and tallow (oil) through a process of size reduction, cooking, pressing and milling.

A typical meat plant processes the equivalent of 150 tHSCW, which equates to 625 head of cattle per day based on a conversion rate of 240 kg of HSCW per head.

Plants can range from domestic kill and chill operations with kill floor/s, boning room/s and no on-site rendering, to fully integrated plants with on-site kill floor/s, boning room/s, rendering and value adding (such as retail-ready products, bone-chip plants, wool scours, hide treating, etc.). The operating hours of plants can vary significantly, from single-shift operations (7am to 3pm) to two-shift operations (7am to 11pm) for the main process areas. The rendering plant extends for a number of hours beyond the main process areas. The following discussion assumes that a plant is operating one or two shifts per day, with some downtime each day for cleaning.

On-site power caseà‚ studies

Rockdale Beef, located at Yanco in southern New South Wales, recently received approval for a grant of AUS $2.1 million ($1.9 million) as part of Round 1 of the New South Wales Energy Saving Fund. The grant was to install a biogas digester to take manure from the feedlot and abattoir, and wastewater from the processing plant to generate electricity. It is anticipated that the 15,500 MWh of electricity generated will be in excess of site requirements, so the excess electricity will be fed back into the electricity grid.

Burrangong Meat Processors in Young in central New South Wales received AUS $700,000 ($622,000) in Round 2 of the New South Wales Energy Saving Fund to recover biogas from their effluent ponds. This will save 3600 MWh of electricity each year, which is 65% of the site’s needs, and is the equivalent of 3500 tonnes of greenhouse gas emissions. This is part of a larger Burrangong Meat Processor programme to become the leader in greenhouse reductions in the meat industry and achieve a position where the plant will become greenhouse-emission neutral.

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