Friday, 29 January 2021

Nitrogen? No gas!

Late enough last night, the BBC picked up a distant death story emanating from Gainesville, Georgia. DD stories are only interesting to the BBC if a) more than 50 people are dead OR b) if one of the dead is British [or Irish if RTE is reporting] OR c) the mode of death is "quirky". Six dead in an Interstate pile-up won't make the cut. Even six dead in a shooting-spree in any part of the US probably won't raise an editorial eye-brow. But asphyxiation? Well that's a story, even if no Brits involved.

The last death by gas story I covered (30 years after the fact) was the leak of methyl isocyanate MIC in Bhopal, India in 1984 which killed more than 2,000 people and disabled at least 10x as many. The insecticide factory where the fatal leak occurred was full of vats containing volatile and toxic chemicals. So it's a bit peculiar that it should have been located in the centre of a densely populated town.

Gainesville is a major centre for the production of USDA approved chicken to service the almost boundless appetite of Americans for meat. And the fatal accident occurred in a Prime Pak plant for processing broiler chickens for the market. Americans are not insensitive people but they are thrifty and don't want to spend more on food than they have to, so they are not, shall we say, encouraged to dwell on how the adorable day old chick became part of their chicken salad sandwich 42 days later. Even the timescale is scarcely credible: from 40g to 900g in six weeks. Economies of scale apply when the product is price-sensitive: Prime Pak employees have to kill and process thousands birds in a batch for the low wholesale-cost business model to work. There has, accordingly, been a lot of research to determine efficient ways of mass killing which a) don't affect the quality of the meat b) don't unduly distress the chickens [in that order of priority].

This is what the HSA Humane Slaughter Association of the UK has to say: "Although the majority of birds slaughtered in UK processing plants are stunned using electrical waterbath systems, an increasing number of plants are killing poultry using gas". You really really don't want to know about electrical waterbath systems whether of not you eat chicken. I can tell you a bit about gas though, because it's The Future. The gas isn't MIC, or zyklon B because those are toxic to both mammals and birds and we are talking about a food product. Gases in the humane slaughter world are those which displace oxygen: either carbon dioxide [remember Lake Nyos], nitrogen or argon usually in a combination dictated by cost and/or legislation. Nitrogen and Argon are inert gases: highly unreactive and so very unlikely to affect the liver and lights of the chicken. We [and chooks] are otoh extremely sensitive to carbon dioxide concentration and our breathing is regulated by that gas far more than by oxygen. High levels of carbon dioxide are extremely distressing and, well, inhumane; as I have witnessed in mice and almost witnessed in humans [I was 40 minutes too late for that event].

Legislation and or best practice guidelines require anoxic gas combinations to be neither more than 30% carbon dioxide nor more than 2% oxygen. Too much oxygen makes the process too drawn out; too much carbon dioxide is offensively cruel. 2% oxygen can be a achieved with a mix of 10% [free] air and 90% argon or nitrogen. Nitrogen is cheaper but argon is denser and better accumulates where the chickens are. And you need all sorts of safety protocols to keep human workers off the killing floor until the gases have been vented /diluted. I'm sorry if this is distressing, I don't eat chicken any more; it's really hard to justify eating meat.

The BBC story signs off with two wholly disingenuous final sentences:  Nitrogen is often used in refrigeration systems. Breathing the gas can be deadly, as it displaces oxygen in the lungs. You may bet your sweet bippy that the nitrogen at Prime Pak was not primarily used for refrigeration. The press officers for Prime Pak and the wider industry will be working really hard to stop the minds of any consumers drifting off towards Oświęcim.

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