; and (B) Predictive Emission Monitoring Systems. (2) Natural gas adjustment Except as provided in paragraph (4), the Secretary shall adjust the carbon intensity determined under paragraph (1) for each generator using natural gas by applying the methane leakage rates assumed in the 9-region MARKAL Database of the Environmental Protection Agency (commonly known as the EPAUS9R database ). (3) Nonemitting generators Except as provided in paragraph (4), the Secretary shall assign a carbon intensity of zero for any generator that does not produce emissions on electric energy generation, including any generator that uses renewable energy, hydropower, or nuclear power. (4) Determination and National Academy of Sciences study The Secretary shall— (A) not later than 180 days after the date of enactment of this section, enter into an agreement with the National Academy of Sciences, under which the Academy shall— (i) evaluate data, models, and methodologies for quantifying lifecycle greenhouse gas emissions associated with generating electric energy from each type of significant source of clean energy, including the sources described in subparagraphs (A) and (B) of subsection (b)(8); (ii) evaluate data, models, and methodologies for determining the appropriate credit value for use in the quantification of Federal clean energy credits under subsection (f) for— (I) qualified renewable biomass, taking into consideration total lifecycle carbon dynamics, including— (aa) carbon absorbed through the regrowth of vegetation; (bb) avoided decomposition relating to the full fuel lifecycle; (cc) carbon sink value from land use changes and temporal changes in forest carbon sequestration; and (dd) lifecycle greenhouse gas emissions, including— (AA) direct greenhouse gas emissions; and (BB) significant indirect greenhouse gas emissions, including all stages of fuel and feedstock production and distribution and feedstock generation or extraction through the distribution and delivery of the finished fuel to electric consumers