An Analysis of the Use of Biosludge as an Energy Source and Its Environmental Benefits in Taiwan

Abstract

Abstract:The objective of this paper was to provide a preliminary analysis of energy utilization from biological wastewater treatment sludge (biosludge) in Taiwan, a densely populated country (estimate 640 persons/km 2 ) with a high dependence (over 99%) on imported energy. The discussion focused on the status of biosludge generation and its management in the years [2004][2005][2006][2007][2008][2009][2010]. Findings showed that the main types of combustible waste (i.e., biosludge) produced by the industrial and agricultural sectors of Taiwan included food processing sludge, wine brewery sludge and agricultural sludge which may be reused as auxiliary fuel in the utilities (e.g., generator, boiler and incinerator). Furthermore, two conceptual biosludge-to-energy systems have been addressed with regard to the thermochemical conversion processes. One is to adopt direct combustion for power generation in the combined heat and power system. Another system uses pyrolysis and gasification for producing biochar (solid fuel), bio-oil (liquid fuel) and syngas (gas fuel). Based on their thermochemical properties and reported generation quantities, the energy potential and the environmental benefits of mitigating CO 2 emissions were also analyzed in the study, showing around 1.1 × 10 3 TJ/year and 57 Gg CO 2 /year, respectively.

A Review of Sludge-to-Energy Recovery Methods

“…As these processes would be discussed in more details in later sections, the dependence of the energy recovery efficiency on the sludge properties requires a brief discussion. As described by past studies on sludge [2,15,21,22], sludge is primarily made up of: (i) water content, which is as high as 98% in the liquid phase and removed primarily by mechanical dewatering to obtain up to 25 wt% solid matter in sticky phase sludge. Further removal can be done via thermal drying to obtain <10 wt% moisture content in dried granular sludge (ii) non-toxic organic compounds which account for up to 48% of the dry solid and are derived mostly from plant sources (characterised by high volatile matter content).…”

The Influence of Allocation on the Carbon Footprint of Electricity Production from Waste Gas, a Case Study for Blast Furnace Gas

“…The study includes emissions related to the building of the infrastructure, the fuel supply chain and the conversion emissions in the electricity plant. Some case studies have shown that allocation rules can have an influence on the calculated impact of bioenergy on the environment [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28]. According to Cherubini et al [29] allocation is important in the bio-energy context because bioenergy systems are often part of multifunctional processes.…”