Back to Basics: Revisiting Blood Collection07 July 2009
Brian Kiepper, extension poultry scientist at the University of Georgia, explains how and why it is vital to collect all blood - even at relatively small processing plants - in order to protect the environment in the University's Poultry Tips (May 2009 issue).
Technological advances in waste minimisation, waste stream analysis and wastewater treatment have focused the environmental efforts of many poultry processing plant personnel on the minutia of pollution prevention. However, it is often a good idea to periodically step back from the small details and revisit the basics. One of these pollution prevention basics is blood collection.
The potential impact of blood on poultry processing wastewater streams is significant. Research shows that blood volume in chickens varies with body weight, with smaller birds having a greater percentage of blood versus larger birds. However, once chickens reach about 4.5 lbs of body weight and above, the percentage of blood in their bodies is about 7.5 per cent.
Once a chicken is electrically stunned unconscious during processing and the throat cut is made, research shows that approximately 50 per cent of the blood in the carcass will drain out. This represents about three to four per cent of total body weight (Barbut, 2002; Raj, 2004; Sams, 2001).
Table 1 shows the potential impact that unrecovered blood has on wastewater based on weight (lbs) and volume (gallons) of blood that is typically bled-out during the slaughter process. The table shows that a processing plant with a daily output of 250,000 small birds must handle 42,200 lbs or about 4,800 gallons of blood a day, wile one processing the same number of large birds must be prepared to recover 70,300 lbs or about 7,900 gallons of blood daily.
|Table 1. Potential weight (lbs) and volume (gallons) of blood impacting poultry processing wastewater streams based on broiler size|
|Bird size||Body weight
|Per cent blood||Blood per bird (lbs)||Birds processed per day||Total wt of blood (lbs)||Total bleed-out weight1||Total bleed-out volume2|
1) Total bleed-out weight @ 50% (lbs)
2) Total bleed-out volume @ 8.85 lbs per gallon
With the advent of larger birds and increased line speeds, many poultry processing plants are now losing blood to wastewater drains where it was not previously occurring. On-site inspections of blood collection systems at Georgia poultry processing plants by University of Georgia (UGA) extension poultry scientists have uncovered new locations of increased blood loss not previously observed. As an example a recent inspection at one Georgia processing plant, where the line speed had increased significantly, revealed two points of new blood loss. At two separate points where the shackle line made 90 degree turns, faster moving carcasses were swinging out and blood was observed falling outside the blood collection trough, which had not been observed when the when processing line ran slower. Increased blood loss has also been observed in plants which have recently converted to processing larger birds.
Key areas identified by UGA Extension Poultry Scientists for periodic inspection of blood collection systems include:
- The transition point between the automatic killer and blood collection trough
- Any bends or turns in the bleed-out shackle line
- The transition point(s) between bleed-out troughs and larger blood collection areas, and
- The transition point between the blood collection system and scalder.
Periodic inspection of these areas will reveal critical need points to increase shielding and minimize floor spillage of blood.
Along with increasing the organic load of the wastewater stream, blood can significantly increase the nitrogen load also. Plants with blood collection systems problems will often see a corresponding rise in TKN (total Kjeldahl nitrogen) levels in their wastewater effluent. Since blood is highly soluble in water, the nitrogen load it contributes to the wastewater stream is not readily removed by physical screening or chemically enhanced dissolved air flotation (DAF) systems, so effective blood collection is critical.
Another significant impact of reducing the amount of blood entering wastewater is in phosphorus reduction, something that is a daily environmental challenge in the heart of the US poultry industry: North Georgia. Following a recent pollution prevention assessment at a broiler processing plant that included UGA Extension Specialists from the Poultry Science and Biological & Agricultural Engineering Departments inspecting the plant's blood collection system, the plant's Environmental Engineer sent an email containing the following passage:
I have great news on the positive results from one of the modifications suggested by your visit. Two months ago, we modified the entrance (right after the auto killer) and exit (right before the scalder) of the 'bleeding flume'. On your visit you pointed out the accumulation of blood spilled on the floor at these two locations due to poor shielding. Well, we did modify it, almost eliminating completely the blood spill in those areas. These modifications have knocked down the total phosphorus entering our wastewater treatment plant about 60 per cent, which resulted on an almost exact reduction of phosphorus at our effluent discharge.
Quick, periodic visual inspections of the blood collection by processing plant personnel can effectively identify blood collection issues on a timely basis and uncover problems that have a real impact on the wastewater stream. Also, experienced wastewater personnel can often alert the production staff on how well blood collection is going by just observing the colour of the wastewater entering the treatment area.
Barbut, S. 2002. Poultry Products Processing. CRC Press, New York, NY.
Raj, A.B.M. 2004. Stunning and Slaughter of Poultry. Chapter 4 in: Poultry Meat Processing and Quality. G.C. Mead, ed. CRC Press, New York. NY.
Sams, A.R. 2001. First Processing: Slaughter thru Chilling. Chapter 3 in: Poultry Meat Processing. A.R. Sams, ed. CRC Press, New York, NY.