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Land Application of Liquid Sludge
Published in Alice B. Outwater, Reuse of Sludge and Minor Wastewater Residuals, 2020
The land application of liquid sludge conforms to the U.S. EPA policy of beneficial reuse of an environmentally acceptable product. Beneficial reuse lowers the net cost to society by diverting sludge from landfills or incinerators. Liquid sludge application provides a method of reusing sludge at minimal cost, reducing the taxpayer burden for sludge management. Farmers that land apply sludge reduce their costs for inorganic fertilizer while adding organic matter to the soil. Even though the land application of liquid sludge benefits both taxpayers and farmers, there are inherent problems to liquid sludge application.
Recent developments in waste tyre pyrolysis and gasification processes
Published in Chemical Engineering Communications, 2022
Athi-enkosi Mavukwana, Celestin Sempuga
Clauzade et al. (2010), Fiksel et al. (2011), Christensen et al. (2007), Silvestraviciute and Karaliunaite (2006) and Corti and Lombardi (2004) conducted a Life cycle assessment of various waste recovery processes. Their analysis showed that from the total energy and raw material balance, waste tyre combustion or substitution in cement production and its use in waste-to-energy processes (incineration) was more advantageous than the other means of managing rubber wastes from an environmental, technical and economical point of view. The worst performing was the cryogenic and mechanical pulverization for reuse as filling materials, because of the high energy consumption related to pulverization processes. Fiksel et al. (2011) and Clauzade et al. (2010) results also indicated that beneficial reuse of waste tyres, particularly in artificial turf, create opportunities to reduce greenhouse gas (GHG) emissions, air toxins, and water consumption. However, the market for artificial turf is saturated, thus limiting its potential for large-scale utilization. Table 3 shows the equivalent kg CO2 emissions per ton of waste tyres for different technologies studied. Energy recovery processes and artificial turf provides, in most cases a significant environmental benefit compared to other technologies concerning emissions savings.
Elevated curing temperature-associated strength and mechanisms of reactive MgO-activated industrial by-products solidified soils
Published in Marine Georesources & Geotechnology, 2020
Dongxing Wang, Xiangyun Gao, Ruihong Wang, Stefan Larsson, Mahfoud Benzerzour
The favorable incorporation of industrial by-products/wastes in soil stabilization as a more innovative and greener option can successfully mitigate the significant environmental impacts related to PC cement production and improve expectedly the efficiency in stabilizing soils. Wild et al. (1998) confirmed the effectiveness of substituting ground granulated blast furnace slag for lime to stabilize sulphate-bearing clay soils in highway and other foundation layers. Kolias et al. (2005) stabilized successfully fine-grained clayey soils by employing high calcium Class C fly ash and Portland cement. Degirmenci et al. (2007) reported the beneficial reuse of two waste by-products of phosphogypsum and fly ash that can provide an inexpensive and advantageous construction product. Hossain and Mol (2011) adopted cement kiln dust and volcanic ash as soil stabilizers, which can provide sustainability to the construction industry. Yi et al. (2015) found carbide slag has a better performance than reactive MgO in activating blast furnace slag to resist magnesium sulfate attack. Rios et al. (2016) stated that the novel materials that are based on sodium silicate-/sodium hydroxide-activated fly ash might have significant advantage in their environmentally friendly nature if compared with traditional PC cement. Wang, Wang, and Wang (2017) proved the effectiveness of reaction MgO hydration reaction in improving the engineering properties (strength, compressibility) of marine soils. Angulo-Ramírez, Gutiérrez, and Puertas (2017) concluded that the alkaline activation of blended Portland cement is highly favorable, and the main products of activated Portland blast furnace slag cement are C-S-H (calcium silicate hydrates), C-A-S-H (calcium aluminate silicate hydrate) and hydrated gehlenite. Deng et al. (2017) proposed a novel and efficient steel slag-based composite material containing steel slag, metakaolin and cement to replace partly traditional Portland cement in deep mixing projects. Okoye, Prakash, and Singh (2017) found the addition of silica fume as a supplementary binder can greatly improve the durability properties of fly ash based geopolymer concrete. Hataf, Ghadir, and Ranjbar (2018) incorporated the chitosan biopolymer to enhance the mechanical properties of soils by promoting the interparticle interaction. Wang, Wang, and Di (2019b) developed a novel cementitious binder based on reactive MgO-activated low-calcium Class F fly ash blend, and revealed the intrinsic mechanisms which lead to the strength gain of MgO-fly ash paste.