While SciTech Connect provides comprehensive coverage of DOE STI, it also covers a great deal of non-DOE scientific research. If you are interested in only the DOE-sponsored research, it is quite easy to limit your search to just DOE-funded research. Using the Advanced Search box and selecting "Matches funded by DOE only" at the bottom should do the trick.
Compare these two searches: Search #1 searches "biomass" in the top box of the Advanced Search. Search #2 performs the same search with the "Limit to Matches funded by DOE only" box checked. Note that in Search #2 the numbers for Everything and Citations are greatly reduced while the Electronic Full Text only goes down a little. This is attributable to the fact that full text in SciTech Connect is almost entirely DOE-funded research.