Managing the carbon footprint of poultry production
By Karen Dallimore
By Karen Dallimore
Bill Van Heyst grew up on a mixed farm near Grand Bend, Ont. He remembers looking after 500 laying hens – that was the maximum amount allowed under quota at the time. He also remembers switching over the old tunnel ventilated 1960s vintage poultry barn to battery cages from free-range. If he’d only known then that free-range would be fashionable once again…
Today, Van Heyst is an environmental engineering professor at the University of Guelph. He describes modern day poultry barns as ‘industrial operations’, with multiple identical structures with the potential of a larger environmental impact than the smaller family type farm of the past.
While much of the Canadian industry is only the size of some of the larger farms in other countries, we do have unique conditions to consider and potential benefits in improving production and management right here at home when it comes to the environmental impact of production.
Inputs and outputs
It comes down to analyzing inputs and outputs, said Van Heyst, which can include species, feed, water and bedding, heating and cooling equipment, electricity and incoming air. Outputs take into account eggs and meat, spent hens and mortalities, litter and excreta and air contaminated with gases, odours and particulates.
Feed and water spills and waste are not only lost money but also, in terms of emissions, water added to soiled manure increases the amount of ammonia volatilized. Excess protein in feed has the same effect. This is something that is being addressed already, said Van Heyst, with diets carefully tailored to the specific stage of production. The ingredients of the diet itself may have a further impact on emissions as well, with omega-3 diets anecdotally resulting in increased odour.
As for bedding materials, studies show no difference in terms of ammonia emissions between chopped straw or wood chips for broilers and turkeys. The choice of bedding remains more of a decision based on price and availability than environmental effect.
What about your production cycle? It’s cheaper to have an empty barn in the winter than the summer. Can you schedule depopulation to a seasonal advantage?
Reducing clean outs may also have an impact. In the U.S., broiler and turkey barns are only cleaned after every two or three cycles. Here, cleaning after every cycle is meant to kill harmful bacteria but is it also killing beneficial bacteria?
The most obvious output is litter and excreta. Ammonia volatilization can be controlled with Poultry Litter Treatment but it’s not cheap, creating a balancing act between cost and effect. Typically, manure will leave the layer barn every three-to-four days on a belt system, ideally going to a separate storage facility where it can be kept dry to crust over to stop volatilization, reducing odour and nitrogen loss as potential fertilizer. Outdoor bunkers typically used for turkey and broiler manure are notorious for nitrogen loss with their backward slope creating a lake in front of the pile.
Energy consumption can be best addressed by conservation. The industry has moved away from incandescent lights to LED while using auto control systems for consistency. A clean barn is more efficient too: It takes more energy to turn a fan caked with a layer of heavy dust than one with clean fan louvers.
The basic cycle of ventilation is fresh air in, contaminated air out. It sounds easy but it is actually difficult when we have to design systems for three completely different seasons: Winter heating, summer cooling and spring and fall somewhere in between – “we’re never quite sure,” Van Heyst says. Thirty-degree swings within a few days are not unusual, creating management challenges.
Reducing ventilation with natural gas heaters may seem like a good way to retain heat in the barn but it also retains CO2, water vapour and possibly carbon monoxide. The trade off for heat loss is air quality. Respirable dust is also a concern for the farmer, causing cardiac and respiratory health issues and exacerbated by ammonia. It’s expensive to control if you go the route of air scrubbers. However, Van Heyst suggests keeping it dry in the house can help.
As an engineer, Van Heyst likes to look to buildings and building materials as potential areas of improvement. Unfortunately, poultry barn design hasn’t been a high priority at the research level. There are new technologies such as heat exchangers, geothermal heating and cooling, composite building materials, structural insulated panels, nanocoatings that can kill viruses and decompose emissions, and phase change materials that store heat in the day and passively radiate heat at night, but no one is bringing these to the farm. How can a barn be designed specifically for cage-free or enriched hens? Products haven’t been designed around that idea either; the battery cages were simply removed.
New barns can be tightened up, said Van Heyst, providing an opportunity to save energy. Good insulation and a vapour barrier will help to retain heat, either from supplementary sources or from the birds themselves. In the summer, peak temperature in a well-insulated barn can be delayed by a few hours to when it’s cooler outside.