Eco-machines are constructions designed for wastewater treatment with the help of plants instead of traditional methods of physical and chemical water treatment. Several ways can assess the efficiency of such systems. Morrison et al. suggest the use of EIO-LCA (economic input-output of the life cycle assessment), which is used for calculation of energy and material input, and emergy analysis applied in the evaluation of work by nature and humans (3). The researches based on these methods are used to evaluate system efficiency and renewability.
Both traditional and ecological water treatment methods require energy input for material transportation. The study conducted by Morrison et al. assessed fossil fuel input for both pre-treatment and post-treatment transportation for an average water treatment plant (16). The results indicated 1 liter of fuel per 1000 liters of sludge transportation and 1.13 liters of fuel per 1 kg of solid waste. (Morrison et al. 16).
The researchers have calculated that 1000 kiloliters of raw wastewater require the input of electricity 1,092 kWh and about 0.87 Gal of fossil fuel (diesel), and provide the output of 686 m3 of treated wastewater (Morrison et al. 16). Shao and Chen concentrated on the comparison of water resource use in ecological wastewater treatment machines and traditional plants (7).
Although water input/output proportion was less efficient in eco-machines due to evapotranspiration, they proved to be efficient in terms of water renewability.
Ecological wastewater treatment methods are considered an environmentally friendly alternative to the chemical and physical ones as they use renewable resources. Although they result in lower water outputs due to evapotranspiration, the evaporated clean water gets into the global water cycle, thus contributing to water renewability. That is why such a method is considered sustainable in terms of its ability to solve the water scarcity problem.
Urban Agricultural Farms
Urban agriculture is a widespread practice of growing vegetables and farm animals within the boundaries of cities. The reason for the existence of such farms is their proximity to the workforce, water supply, and consumers. Rogus and Dimitri analyze the specificity of these farms in the USA and conclude that they are smaller in size than rural ones, as the average urban farm area is 174 acres, while rural farms are 418 acres (65).
Currently, many urban farms are developed as nonprofit enterprises used for socially-oriented purposes, such as education or promotion of eco-friendly practices. However, the input/output analysis shows that they are efficient and can serve as the resource for local food security.
Agriculture can be viewed as the process of energy conversion with measurable efficiency. McDougall et al. suggest using the approaches of energetic and economic analyses for the assessment of urban farming input/output ratio (2).
The researchers have conducted a study of 13 urban farms and calculated monetary inputs, as well as inputs of work in the production of 62 varieties of products (McDougall et al. 3). The inputs of financial resources per kilogram of produced food were estimated at $USD28.53, exceeding the average purchasing costs of 53 product categories out of 62 (McDougall et al. 3).
However, average yields were significantly higher in urban farms (5.94 kg/m2), comparing to rural farms that yield an average of 3.18 kg/m2 (McDougall et al. 3). Mean energy input was estimated as 3.16E + 7 sej, which is a positive relationship (McDougall et al. 3). Despite high economic costs, urban agriculture proved to give high yields and can be effective with proper resource optimization.
Moreover, urban farming has a positive effect on the environment as its proximity to consumers helps to reduce emissions caused by the transportation of products. In addition to this, foods grown in urban areas can be consumed right away without the expenditure on storage facilities. It has the potential to facilitate carbon sequestration improving the urban atmosphere and reduce water waste primarily used for lawn maintenance.
Works Cited
McDougall, Robert, et al. “Small-Scale Urban Agriculture Results in High Yields but Requires Judicious Management of Inputs to Achieve Sustainability.” Proceedings of the National Academy of Sciences, vol. 116, no. 1, 2018, pp. 129-134. Web.
Rogus, Stephanie, and Carolyn Dimitri. “Agriculture in Urban and Peri-Urban Areas in the United States: Highlights from the Census of Agriculture.” Renewable Agriculture and Food Systems, vol. 30, no. 1. 2014, pp. 64-78. Web.
Morrison, Marc, et al. “Complementary Life Cycle Assessment of Wastewater Treatment Plants: An Integrated Approach to Comprehensive Upstream and Downstream Impact Assessments and Its Extension to Building-Level Wastewater Generation.” Sustainable Cities and Society, vol. 23, 2016, pp. 37-49. Web.
Shao, Ling, and G.q. Chen. “Embodied Water Accounting and Renewability Assessment for Ecological Wastewater Treatment.” Journal of Cleaner Production, vol. 112, 2016, pp. 4628-4635. Web.