Regulatory Promotion and Benefit Analysis of Biogas-Power and Biogas-Digestate from Anaerobic Digestion in Taiwan’s Livestock Industry

Abstract

The objectives of this paper were to summarize the status of the livestock (pig and cattle) industry and its waste management in Taiwan. The Water Pollution Control Act authorized the reuse of liquor and digestate from anaerobic digestion (AD) as fertilizers for agricultural lands on 24 November 2015. A large number of official databases and literature have been surveyed and analyzed to address the characterization of the biogas (AD-based) digestate and the potential benefits of biogas-to-power in Taiwan. On the promulgation of the Act, the central ministries have jointly managed the applications of livestock farms for reusing the AD-based liquor and digestate as fertilizers for farmlands. The survey findings revealed that the biogas digestate from a pig farm in Taiwan contained significant amounts of nitrogen, phosphorus, and other soil nutrients such as calcium and magnesium. However, it is necessary to control zinc present in the biogas digestate from pig-raising farms. A preliminary analysis based on 123 large-scale pig farms with a total of 1,223,674 heads showed the annual benefits of methane reduction of 6.1 Gg, electricity generation of 3.7 × 107 kW-h, equivalent electricity charge saving of 4.0 × 106 US$, and equivalent carbon dioxide mitigation of 152.5 thousand tons (Gg). Obviously, the integration of AD and biogas-to-power for treating animal manure is a win-win option for livestock farms to gain environmental, energy, and economic benefits.

Valorization of Value-Added Resources from the Anaerobic Digestion of Swine-Raising Manure for Circular Economy in Taiwan

“…Because swine excrement and manure contain lots of organic matter and dissolved nutrients, the wastewater from swine-raising farms before discharging into water bodies must be treated to avoid serious pollution of receiving streams. In the past, the three-step wastewater treatment system (i.e., liquid-solid separation, anaerobic digestion, and aerobic treatment) has been successfully adopted in Taiwan for additional biogas-to-power generation [5,7,11]. In most cases, the discharge of treated swine-raising wastewater can meet the effluent standards, which will be described thereafter.…”

“…On the other hand, biogas digestate is another value-added resource produced from the anaerobic digestion at the bottom because it contains valuable nutrients for plant growth and crop production as an organic fertilizer [2]. It should be noted that heavy metals may be found in biogas digestate and/or swine manure, causing it to be easily leached from soil of fertilized farmland [3][4][5]. In addition, the wastewater from the swine-raising farms without adequate biological treatment may cause adverse impacts on surface water quality and air quality by the eutrophication and the odor, respectively.…”

“…As compared to the traditional three-step system [7], the swine-raising wastewater directly treated by the anaerobic digestion not only creates biogas for power generation, but also produces the value-added resources (i.e., liquor and biogas digestate) for farmland fertilization [5,8]. In Taiwan, the central ministries, including the COA, the EPA, and the Ministry of Economic Affairs (MOEA), have provided economic and financial supports under the regulatory promotion.…”

Promoting the Circular Economy via Waste-to-Power (WTP) in Taiwan

“…This biogas-to-power system installation fee includes the expenditures for the biogas purification system, the power generator, and related engineering items (e.g., pipework and foundation). On the other hand, the FIT rate of biogas-to-power adopting the AD processes in 2018 was as high as 5.0161 NTD $/kW-h ($US 1 ≈ 30 NTD$) [26].…”

Enhancing Anaerobic Digestion: The Effect of Carbon Conductive Materials

“…On the other hand, anaerobic digestion is capable of generating biogas which can either be used directly or converted into energy by the use of a combined heat and power (CHP) unit, the process also produces stabilised organic material as a by-product which can be valorised as an organic amendment. This digested material is a nutrient-rich sludge which can serve as a fertiliser, if it is well handled by proper application operation and control of heavy metals in soils [2].…”