NOVELTY - Increasing (M1) methane production in landfill (202), involves passing one or more gases comprising methane produced in landfill through generator, operating generator to produce electric current, and recycling first portion of exhaust gas (212) stream to landfill.    USE - The method (M1) is useful for increasing methane production in a landfill. The method (M2) is useful for producing biodiesel, FAME or biofuel from one or more algal species e.g. diatoms, green algae, blue-green algae and golden-brown algae. The system (S1) is useful for producing biodiesel or biofuel. The system is useful for generating electric current (all claimed).    ADVANTAGE - The method enables production of methane with reduced emission of noxious gas. The systems are suitable for industrial applications.    DETAILED DESCRIPTION - Method (M1) for increasing methane production in a landfill, involves passing one or more gases comprising methane produced in landfill through generator, where generator is methane powered generator (208), operating generator to produce electric current, where operation of generator produces exhaust gas stream comprising water, carbon dioxide and carbon monoxide at elevated temperature, and recycling first portion of exhaust gas stream to landfill, where recycled gas stream increases temperature and moisture content of landfill, and thus increases methane production. INDEPENDENT CLAIMS are included for the following: (1) methane gas (206) produced by the above-mentioned method (M1); (2) method (M2) for producing a biodiesel or a biofuel from one or more algal species, involves providing one of more algal species with one or more nutrients in cultivation tank (214), passing gas stream comprising one or more components chosen from water, carbon dioxide and carbon monoxide at elevated temperature through cultivation tank to cultivate algae, transferring cultivated algae (216) to biodiesel production tank, where cultivated algae produce algal oils or lipids in presence of carbon dioxide, nutrients and light under aerobic conditions, and converting algal oils and lipids to biodiesel or biofuel using transesterification reaction in biodiesel production tank, where the algal species are chosen from diatoms (bacillariophytes), green algae (chlorophytes), blue-green algae (cyanophytes), golden-brown algae (chrysophytes), haptophytes, freshwater algae, saltwater algae, Amphipleura, Amphora, Chaetoceros, Cyclotella, Cymbella, Fragilaria, Hantzschia, Navicula, Nitzschia, Phaeodactylum, Thalassiosira, Ankistrodesmus, Botryococcus, Chlorella, Chlorococcum, Dunaliella, Monoraphidium, Oocystis, Scenedesmus, Nannochloropsis, Tetraselmis, Oscillatoria, Synechococcus, Boekelovia, Isochrysis and Pleurochrysis; (3) biodiesel (222) or a biofuel produced by the method (M2); (4) system (S1) for producing a biodiesel or a biofuel from comprising cultivation vessel or tank for growing the algal species in growth medium in presence of nutrients, where tank or vessel comprises one or more inlets or conduits to allow passage of gas stream at elevated temperature, harvesting vessel for harvesting cultivated algae from the biodiesel production tank, concentrating tank for concentrating algae by removing growth medium, lysing tank for releasing produced algal oils or lipids by lysing the algal species, separation vessel for separating released algal oils or lipids from other cellular components, and reaction vessel for converting separated algal oils or lipids to biodiesel, fatty acid methyl ester (FAME), biofuel or their combinations and modifications by transesterification reaction; and (5) system (S2) for generating electric current comprising one or more waste management units, where the waste management units produce one or more gases comprising methane, and one or more gas flares or gas stacks (204) placed in or attached to the waste management units, the gas flares or gas stacks are in fluid communication with a methane powered generator, and the operation of the generator in presence of methane in the one or more gases generates the electric current.    DESCRIPTION OF DRAWING(S) - The drawing shows zero-discharge landfill.    Landfill (202)    Gas flares or gas stacks (204)    Methane gas (206)    Methane powered generator (208)    Exhaust gas (212)    Cultivation tank (214)    Cultivated algae (216)    Electric grid (220)    Collection vessel (224)