Accessibility of pores in coal to methane and carbon dioxide

► We demonstrate that SANS and USANS can be used for evaluating volume of closed pores in coal. ► We study the accessibility of pores to CO2 and CH4 in three different coals as a function of pore size. ► The volume fraction of accessible pores varies between ∼90% and ∼30% depending on the pore size. ► Accessibility of coal pores is distinctive for each of the examined coals.