Life cycle analysis (LCA) was used to estimate the nonrenewable
primary energy requirement (GJ/GJ) and greenhouse gas emissions
(kg CO2 eq./GJ bioenergy) for produced bioenergy in four scenarios
(Fig. 1). Scenario 1 consists of (a) anaerobic digestion of dairy
waste, (b) algal biodiesel production using effluent from [a], (c)
anaerobic digestion of algal biomass left after lipid extraction
and recycling of nutrients to the step [b], (d) application of solid
fraction from step [a] and [c] on the agricultural field. Scenario 2
consists of step [a] to [c] of scenario 1, sludge from step [a] and
[c] was processed through pyrolysis and biochar generated from
pyrolysis was applied on the agricultural land. Scenario 3 is similar
to scenario 1, but, instead of applying sludge on the agricultural
field, sludge was enzymatically hydrolyzed and used for algal biodiesel
production (data used for enzymatic hydrolysis and algal
biomass production are given in Table 1). Residue remaining after
hydrolysis was applied on the agricultural field as a soil amendment.
In scenario 4, in addition of all the processes applied for scenario
3, pyrolysis was used to process residue from enzymatic
hydrolysis and produced biochar was applied on the agricultural
land as a soil amendment.