Introduction
Canada does a poor job of recovering nutrients that can be used in food production. The dependence on synthetic fertilizers is in part the result of this failure. the bathroom should be considered part of the food system. Nutrients are lost because of inefficient collection and recovery from compost and sewage sludge. “In Canada, approximately 30-40% of all municipal solid waste is composed of organic material" (Forkes, 2011, p 62) Many regions do not have backyard, residential curbside or commercial composting programmes. Those that do, often have inefficient composting processes, with losses and poor quality end-product that is not used for food production. Regarding human waste, we excrete up to 90% of the total protein consumed. “Lind et al. (2001) estimated that the recycling of nutrients present in domestic wastes could replace 35-45% of fertilizers needs, 20-25% from the recycling of nitrogen in urine alone.” (Forkes, 2011, p. 63) Only about 20% of mined phosphate rock actually makes it to our food, with urine and feces losses a significant part of the inefficiency (Ashley et al., 2011). Unfortunately, most municipal sewage is contaminated with industrial materials, microplastics, drug metabolites and cannot be applied safely to farmland (although the practice continues). As a result, incineration, composting and landfill are the most common alternative disposal methods. Canada produces about 660,000 dry tonnes of biosolids annually and about half of that is applied to land, including farm fields. At this point, there is no practical way to eliminate microplastics from sewage sludge as it would require elimination of plastics from clothing in particular (Helmore, 2023).
more than 125 wastewater treatment plants in all provinces are generating biomethane. Canadian Biogas Association estimates that biodigestion and landfill-gas recapture systems are generating less than 4 per cent of the total potential biogas energy. wastewater of roughly 84 per cent of the population is treated at a basic level (primary treatment) or better. Nelson, B. 2022. Canada is wasting its waste. It’s time to harness one of the world’s most squandered natural resources. G&M Oct. 8.
See Gasman for effluent and sewage discharge regulations
Consistent with metabolic rift theory, returning urban nutrients to farms will likely be essential for sustainable food production. Though not well studied at this point, a case study analysis of European organic farms suggests that non-agricultural inputs for N, P and K, including composted municipal and industrial waste, digestate from communal biogas plants as well as commercially sold biological fertilizers, will all be important nutrient sources for balancing key macronutrients, and there is relatively positive acceptance of such sources from farmers themselves. At this point, sewage sludge is not permitted in European organic standards, so unsurprisingly it is not well accepted as a nutrient source (Reimer et al., 2023)
Efficiency
Sewage sludge and humanure application to land to close nutrient and energy loops
Separating sewers in established communities
Many neighbourhoods in Canadian cities were built with combined sewer outflows (CSOs), rather than separate piping for household waste water and storm runoff. For example, in the older parts of Scarborough in Toronto, most houses were built with CSOs, and from the 1960s, new subdivisions were constructed with separate systems. By 2008, approximately 35% of the area had combined sewers, 45% had partially separated sewers[1] and only 20% was separated[2]. Compounding this problem, many commercial facilities also have CSOs. Commercial and residential downspout disconnection programmes have helped reduce, at a relatively low cost, the number of partially separated systems. However, fully separated systems are expensive to create from CSOs, and progress has been slow, dependent particularly on capital budgets. In Toronto’s case, the municipal government has a 25-year Master Plan to improve stormwater management and sewer systems.
Continuing the process of pipe separation of industrial from residential and elimination of contaminants and of residential CSOs are critical strategies.
[1] In a partially separated system, street stormwater is carried off separately, but household stormwater ends up in the household waste water pipes.
[2] Public education materials from a 2008 public consultation on sewage separation in Scarborough sheds light on this, http://www1.toronto.ca/city_of_toronto/policy_planning_finance__administration/public_consultation_unit/toronto_water/scarborough_waterfront/files/pdf/2008-06-16_posterboards.pdf
Substitution
Human and animal inedibles for compost and industrial applications
Curbside collection programmes: residences, MURBs and commercial establishments
Municipal planning departments should require new multi-residential buildings to have organic waste collection infrastructure incorporated into their design. The hope is that such initiatives will be mandated to municipalities by the Ministry of the Environment and Climate Change (MOECC) as part of the organic waste action plan under the new Waste-free Ontario Act.
Landfill ban
In Ontario, municipal and/or local governments can regulate waste management and recycling activities through their by-laws, including setting in place landfill bans (restricting what materials can be landfilled)[1]. The new provincial Waste-free Ontario Act also sets the stage, within the Strategy required by the province, to enact disposal bans.
A number of other jurisdictions have undertaken such initiatives. The government of Nova Scotia enacted a landfill ban for all organic waste in 1998 (Friesen, 2000), and currently, a negligible amount of organic waste is sent to the landfills. This ban led to further implementation of the compost and biogas industries; however, Nova Scotia is currently struggling to send its organic waste to such facilities because the infrastructure was not set up efficiently when the ban was enacted. The Regional District of Nanaimo has a ban on commercial organic waste[2]. Metro Vancouver brought in an organic disposal ban on January 1, 2015, with an effective date of July 1. The staff has noticed an increase in depacking services, organic pick up services, and a 10% improvement on tonnage going through local composting facilities. Restaurant and institutional food service source separation systems have increased dramatically. Although enforcement is an ongoing challenge, and fines are still being levied, organics are down from 36 to 28% of the waste stream (Marr, 2016). Massachusetts implemented a ban in 2014, and Vermont has set one to begin in 2020 (Specht, 2013).
Ontario would have a difficult time implementing a province-ban in the short term. However, as a substitution stage strategy, many changes to waste reduction infrastructure and management will have already been implemented before a landfill ban is enacted, making it more feasible.
Sewage sludge and humanure application to land to close nutrient and energy loops
Nutrient removal technologies
Numerous technologies have been used, and others are under development, to remove nutrients from sewage sludge and urine and make them available to the fertilizer industry. For example, “even among facilities not currently regulated for specific numeric criteria, many have the capacity to remove as much as 20 to 50 percent of their current nitrogen load through minor process changes that require little capital investment.” (The Johnson Foundation, 2014, p. 8)
This approach avoids the problems associated with spreading biosolids, and consequently is an intermediate stage strategy. Struvite is one of the best developed products, rich in P, Mg, and N. Precipitation, thermal treatment, crystallization, separation and wet chemical processes have been used to extract nutrients, in research and/or in practice (Water Environment Research Foundation, 2011). Some 30 nutrient recovery processes have been identified (Cordell, Rosemarin, Schröder, & Smit, 2011) and many others are at the assessment stage with questions such as: how efficiently does the process extract nutrients; at what quality, financial and resource cost; and what kinds of revenues they can generate to balance against costs, what kinds of regulatory environments might favour recovery? Public utilities will need support to test and implement these systems. P cycle, human history and struvite (Rosen, 2021, the Atlantic)
Small scale/decentralized sanitation systems in smaller new settlements
In new small settlements, some of which are deliberately positioned as eco-village designs, there are opportunities to rethink the traditional approach to sanitation systems. Ranging from individual household onsite systems to community-level designs, many have proven to be feasible at lower cost, and may better serve remote or low-density populations. Many also are able to dispose of treated or untreated excreta/wastewater on land because humanure is not contaminated with industrial pollutants (Cordell et al., 2011).
Change code rules to permit more composting toilets and solid (rather than wet) sanitation systems
Austin Texas may be one of the few cities in North America that permits composting toilets (Price, 2009). There are substantial issues with dispersion of the compost. However, the Ontario Building Code appears to permit them under Class 1 of its five classes of sanitary sewage and disposal: a chemical toilet, an incineration toilet, a recirculating toilet, a self-contained portable toilet, and all forms of privy including a portable privy, an earth pit privy, a pail privy, a vault privy, and a composting toilet system, all of which can receive only human waste.
[1] For details on how waste is regulated in Ontario, see https://www.rco.on.ca/how_waste_is_regulated
[2] The by-law is available at: http://www.rdn.bc.ca/cms/wpattachments/wpID98atID2047.pdf
Redesign
Sewage sludge and humanure application to land to close nutrient and energy loops
Sewage water, nutrient and energy recovery and distribution
At the redesign stage, sewage treatment facilities shift from being waste disposal locations, to water, nutrient and energy recovery and distribution centres. While there are now many tremendous examples of improved overall effectiveness regarding treatment and reduction of discharges,
the public health and environment-based model of the ‘traditional’ wastewater treatment utility that evolved over the last 150 years has had as its principal objectives, to collect and transport human and industrial waste-water quickly and as far downstream as possible to central treatment works that could purify it sufficiently and cost-effectively so that when discharged, receiving waters would meet applicable environmental standard (National Association of Clean Water Agencies (NACWA), the Water Environment Research Foundation (WERF) and the Water Environment Federation (WEF), 2013, p. 5)
Within an agroecological framework, the focus shifts to closing the nutrient loops while sustaining or improving sanitation and public health objectives. For example, some analysts believe 100% recycling of P from waste systems will be required to avert a P availability crisis in the long term (Ashley et al., 2011). This objective would need to be implemented in association with many other measures proposed here that have significant P use efficiency and recovery dimensions (Cordell et al., 2011).
According to one report,
examples of cross-cutting, functional goals for nutrient management include:
- maximizing the capture and reuse of waste stream nutrients;
- minimizing the energy used to process wastewater;
- minimizing nutrient release into the environment;
- minimizing alternations to the hydrological cycle;
- minimizing the release of GHG emissions from infrastructure; and
- maximizing economic benefits. (The Johnson Foundation, 2014, p. 5)
On a decentralized scale, households would need to be designed with urine separation and dry household solid waste systems, obviously with huge implications for household design, building codes and neighbourhood waste management systems. A key additional challenge is moving nutrients to farms. Given existing built infrastructure, such redesigns may only be feasible in the construction of new neighbourhoods and communities that are integrated with food production. The possibilities have been explored in Magid, Eilersen, Wrisberg, & Henze (2006).
Vancouver uses it's biosolids - Nutrifor - on grazing land, dramatically improved soil quality and forage production
