Table 2: Summary of LFG utilisation [²⁸].

LFG Utilisation	Discussion	Advantages	Disadvantages
As a source of natural gas	This involves the upgrading of LFG into natural gas quality [29]. A study investigated on the upgrading of LFG using a high-pressure water absorption process [30]. The study showed that using high pressure gas absorption technique, LFG can be improved to 87.9 ± 2.0% methane contents [31]. This refined LFG can be used in the natural gas network for domestic purposes. Developed nations such as the US and Europe nations commercially use LFG in place of the conventional fuel which has been used for domestic purposes [28].	Can be used domestically for cooking and in industries as a source of heat. Can be used in generation of revenue for the government, when sold. Used in natural gas pipelines.	Relatively expensive and requires LFG expensive processing techniques.
Boiler System	This technique is the second most common use of LFG. Boilers use LFG as a source of fuel for production of steam and hot water. In addition, the steams formed from the process can be used for heating buildings, schools, hospitals and even providing steam for large manufacturing industries (pulp and paper industries). Examples of landfill that uses LFG for boiler system are the Gaoantun landfill (Beijing, China), and three rivers regional landfill (South Carolina, USA) [28].	Relatively not expensive. Does not require large amount of LFG when processing. Can be used in landfill sites, schools, hospitals as a source of heating. Can make use of maximum amount of LFG collected.	Accessibility of end-users must be close by. The cost is tied to length of pipe lines.
Furnace, dryers and kilns	This involves the direct use of raw LFG from landfills as a source of fuel directly from the kilns [29]. Manufacturing companies that produce cements, ceramics, iron, wood and steel uses LFG directly from the landfill site as a source of fuel for infra-red heating mechanism. The infra-red heating can reach up to 800°C - 1000°C with efficiency up to 93% [28].	The raw LFG can be used directly from the kilns in some manufacturing companies. Inexpensive and easy to install.	Constraint of LFG utilisation, if used seasonally.
Use as vehicle fuel	LFG are compressed and used as a source of fuel for powering vehicles. A study shows that the collection, purification drying and compression to acceptable pressure gauge of raw LFG can be used as fuel for vehicles [32]. This process is being utilized in some Africa nations but the process is not favourable in all nations. For example, Global Infrastructure Basel company carried out a project to convert LFG into vehicle fuel for fleet vehicles in the Ekurhuleni metro Municipality of South Africa. The project extended for one year and costed USD 5 million [33]. Before the production as vehicle fuel, it is advisable the project owners verify the tax system for vehicle fuel and other variables, to calculate if the project will be profitable or not [29].	Use as a source of fuel to landfill vehicles and trucks. Can also be used as a source of revenue to the government when sold.	Can be expensive due to the processing of the raw LFG collected into vehicle fuels
Use as a source of electricity	LFG can be used as fuel for power generation which can generate electricity up to 45 megawatts from a steam engine; this is the most common use of LFG utilisation technology [29]. A study analysed different methods to generate electricity and recent innovative technologies from LFG; some of these technologies included, reciprocating internal combustion engine, use of gas or steam turbine, power plant with organic rankine cycle, Stirling cycle engine, molten carbonate fuel cells and solid oxide fuel cells, the selection of method is owed to several conditions [34]. This form of utilisation has shown to be reliable, environmentally and economically friendly to its users [28]. A typical example is the Durban LFG plant in eThekwini Municipality South Africa.	Can be a source of electricity. Can be used as a source of revenue to the government due to the sale of the electricity generated. Maximum use of LFG, when the LFG is collected from the landfill site.	Relatively high cost of operations. Requires high level of expertise and technology. Cost may be negligible with countries with low electricity costs.