Potato, pot-ah-to: can we feed cull potatoes to reduce food waste and produce high quality beef?  

Background

Upcycling food waste as animal feed is one of the main strategies crop and livestock producers use to reduce waste and use it to produce nutrient dense beef. Using food waste as livestock feed also has the potential to lower the negative environmental and health impacts that are common in other food waste mitigation strategies like composting and anaerobic digestion. However, recycling food waste as feed is not without its challenges. From a Canadian perspective, challenges are mainly related to access. The wide geographic range of cattle and crop production sites can rack up high transportation costs, there are regulations that limit the potential use as feed, and overall economic feasibility can all be limiting factors. However, potatoes are not subject to restriction by CFIA and can serve as a model to show the potential environmental benefits of upcycling food waste to ruminants.  

Potatoes are widely grown in Canada producing and average of 5.3 MMT annually. Waste from potato production is mainly in the form of cull potatoes. That means perfectly good potatoes thrown out due to limited storage space, imperfections not desired by consumers among other things, though they are still considered a high energy source for ruminants. Potatoes contain 77% total digestible nutrients (TDN), 10% crude protein (CP), 11% neutral detergent fibre (NDF), 7% acid detergent fibre (ADF), making them desirable for finishing cattle rations as partial substitute for grains.  

In Canada, potato waste has been used to improve feedlot cattle performance for years, but little research has explored the potential positive effects on the environment and producer’s bottom-line. Therefore, the objective of this study was to examine the effect of partially substituting grains with cull potatoes in standard feedlot diets on feed conversion ratio, land use, net GHG emission and the cost of production. This proposed study will utilize data gathered under Canadian feeding management, prices, and marketing conditions for feedlot finishing production systems, and will be used as a model for other sources of food waste. 

Objectives

• Determine if using cull potatoes (food waste) as a partial substitution for grains in beef cattle finishing diets to improve environmental impacts, cost of production and livestock performance.  
• Evaluate potatoes as a potential model to estimate the environmental, economic and productivity impacts of utilizing other food waste as livestock feed in Canada.  

What They Did

This team complied a literature review to inform on food loss, food waste, and by-products in Canada to understand the current state of the system and the current/potential role cattle can play in upcycling these products. This included potato waste availability, price, inclusion level etc. in both Western and Eastern Canada.  

This team looked at the outputs to analyze and compare production factors, environmental parameters and economics which included the future monetary cost of GHG emissions as outlined by the Manitoba provincial policy. Estimations were made for calf-fed, yearling-fed or yearling grass-fed heifers or steers supplied with potato waste at 0% (standard diet), 15%, or 30% dietary dry matter. In brief, GHG emissions were assessed using the methods and algorithms of the HOLOS model and other coefficients, especially, for the purchased feed.  

What They Learned

Across cattle categories in the west, total GHG emission intensity was reduced by 2.1-4.8% with 2.36, 2.31, and 2.24 kg CO₂e/kg live weight, for the standard diet, 15% and 30% potato inclusion, respectively. Similarly, reduction in the east was 2.2-4.6% with 1.65, 1.61, 1.57 CO₂e/kg live weight, for the standard diet, 15% and 30% potato inclusion, respectively. Although potato waste inclusion reduced net farm emissions due to decreases in direct, indirect and energy emissions (mainly from cropping), it also resulted in higher methane emissions as a result of lower dietary total digestible nutrients. Using potato waste also reduced land required for feed production by 16% and 31% (west) and 14% and 28% (east) at 15% and 30% inclusion, respectively. Results suggest that feeding potato waste could reduce GHG emissions through significant reductions in land area required to produce grain in standard feedlot diets. Furthermore, utilization of potato waste in cattle diets re-directs waste away from landfills, mitigating emissions and eliminating disposal cost, while producing high quality animal protein.  

What It Means

Repurposing the “waste” of other agricultural industries as feed for beef cattle is a huge opportunity to reduce the inputs that are required to produce local food in Canada. Potatoes that would not make it to the human food market have been used as a means to effectively supplement crop grains like barley and corn to produce high quality beef while reducing the land, GHG emissions, land use and costs of both systems. What this truly means is we can use cattle as a means to upcycle food that people cannot or will not eat, providing more food on Canadian’s plates and reducing negative environmental impacts from food crops, grain crops and animal production.