id	keyword
brj-23562	biogas
brj-23562	upgrading
brj-23562	biogas upgrading
brj-23562	papers
brj-23562	research
brj-23562	et al
brj-23562	number
brj-23562	doi
brj-23562	field
brj-23562	terms
brj-23562	network
brj-23562	analysis