Cost–Benefit Analysis of Municipal Sludge as a Low-Grade Nutrient Source: A Case Study from South Africa

Abstract

Municipal sludge has economic value as a low-grade fertilizer as it consists of appreciable amounts of the macro and micronutrients. When using sludge as fertilizer, the economic aspect should be taken into account. In this study, the following specific objectives were identified: (a) to investigate the economic feasibility of using sludge as a fertilizer; (b) to estimate the maximum economic distance sludge can be transported as a fertilizer; and (c) to test the economic feasibility of selling sludge using commercial inorganic fertilizer as a bench mark. The study showed that for anaerobically digested, paddy dried, municipal sludge consisting of 3% N, 2% P, and 0.3% K the economic feasibility of transporting the sludge was limited to a diameter of 20 km in the arid zone, 28 km in the semi-arid zone, 51 km in the sub humid zone, 66 km in the humid zone, and 75 km in the super-humid zone. Therefore, the economic feasibility of using sludge as a substitute for or complementary to commercial inorganic fertilizer is dictated by the distance between the wastewater care work and the farm, sludge nutrient concentration, agro-ecological zone (rain and temperature), and the real-time commercial inorganic fertilizer price.

Blended Sewage Sludge–Palm Kernel Expeller to Enhance the Palatability of Black Soldier Fly Larvae for Biodiesel Production

“…Next, the operating cost which will be expensed annually is calculated from electricity, chemicals, water system, and other utilities used in the plant. The transportation cost (T) will mainly depend on the distance between the sewage sludge and PKE collection points and the BSFL-based biodiesel processing line (D), the number of loads (N), and the rate of the truck (r) as shown in Equation 6 [66]. Finally, the product cost, i.e., biodiesel in this case, is influenced by the feedstock cost, plant size, and value of glycerin by-product.…”

“…Indeed, the worthiness investigation for larval biodiesel production should also cover the calculations of the whole industrial scale that can be simulated using ASPEN PLUS software [68]. Furthermore, both investment and transportation costs could not be precisely determined in this study, since the investment cost depends on each plant, and transportation cost will be calculated based on the agreement between plant and transporter [66]. In the case of product cost, the biodiesel price would be calculated based on B7 (7% blended biodiesel) price since this is a current biodiesel mandate in Malaysia's industrial scale [69].…”

Microwave and Ultrasound Based Methods in Sludge Treatment: A Review

“…During the treatment of wastewater in a wastewater treatment plant, an excessive amount of wastewater sludge is produced. The resulting sludge can be and is used for either fertilization purposes [16,17] or anaerobic digestion (AD), i.e., biogas production. The product of the AD, as discussed in the Introduction, is mainly methane and carbon dioxide.…”

Efficiency and factors for agricultural use of sludge in circular Bulgarian economy

“…Arround the globe, there are numerous studies on the factors and efficiency of sludge use in agriculture (Barbu, 2012;Daniels, 2011;Iticescu et al, 2021;EC, 2008;2021;Ekane et al, 2021;Hudcová et al, 2019;Rosiek, 2020;Rosemarin et al, 2020;Scozzari and Mansouri, 2011;Taşeli, 2020;Tesfamariam et al, 2020;Usman et al, 2012). Interest in this area is growing even more in connection with the new challenges related to environmental pollution, climate change, protection of human and animal health, the current COVID pandemic and others.…”