All the oil's have variables , one plant will produce more or less oil , gliserin , also will have varying of gases when burnt / exhaust ,
I was reading the other day something about soy producing more of one of the exhausts that are termed to be bad or to be measured when , or if diesel emission testing comes around .
Something els to consider , if growing is some crops will , or will not have more issues , harder on the land , may cost more because of more or less chemicals needed to grow .
What is your issue ?
Are you getting from a fuel station / processor / farmer group ?
It seems that by the time any access near our metro area , the is little or no knowledge of the fuel except price .