Advances in Biogas Technology - Biotechnology in China: Biofuels and Bioenergy - page 134

completed. Table 6 summarizes the large and medium-sized municipal solid waste
biogas plants running or under construction in China [ 35 ].
Despite much progress achieved in recent years, there are still many challenges
in the practical application and promotion of landfill biogas technologies.

1. The high cost of power output is a big problem. Usually landfills do not have a
power transmission system. Therefore, selling electricity generated from the
landfill gas power system requires permission from the power company. This
procedure is necessary to make landfill electricity output legal and standard in
internet protocols, but practically it can be very complicated. Thus, the price of
landfill-derived biogas cannot compare with that from other conventional
sources.
2. Lack of operational economic incentives. Although the Chinese government
has introduced some economic incentive policies to promote the development
of renewable energy, including landfill gas power generation, there still exist
many problems in policy implementation, such as lack of grid access permis-
sion, standard power purchase agreement and electricity price calculation
method, etc.
3. Lack of Chinese-made special equipment for power generation from methane.
For example, the landfill gas power generation equipment in Tianziling,

Hangzhou was purchased from an American company.
4. Difficulty in popularizing the technology. Unstable landfill biogas production
increases the difficulty in estimating the power-generation capability and

controlling the practical power generation operation.

3 Emerging Technologies

3.1 Anaerobic Membrane Reactor

The anaerobic membrane bioreactor (AnMBR) was initiated in 1978. COD removal
of 90% and NH 3 -N removal of 75% were achieved in an early system that integrated
an anaerobic nitration pool and a membrane system for sewage treatment. Incor-
porating the membrane separation technology into the anaerobic process brings
many advantages. In such a system, the hydraulic retention time (HRT) is uncoupled
from the solid retention time (SRT), and thus high biomass concentration can be
maintained under high hydraulic load and sufficient mixing, which ensures high
treatment efficiency. Due to the high biomass concentration and sufficient retention
of some slow-growing microorganisms, the AnMBR generally has good toxic
resistance, and is especially suitable for the treatment of high organic-load and
biorefractory wastewater, such as industrial wastewater and landfill leachate.
The biological treatment unit of the AnMBR usually adopts UASB, fixed-bed,
fluidized-bed

and two-phase-type reactors. Compared to aerobic MBR, the