Practice Guide). Each annotation is identified by a sequential reference number. For F-notes, M-notes and X-notes, the number also appears in bold superscript at the relevant location in the text. All annotations contain links to the affecting legislation. (a) use waste belonging to the authority for the purpose of producing from it heat or electricity or both; (b) establish and operate, within or outside its area, such generating stations and other installations as the authority thinks fit for the purpose aforesaid; and (c) where the authority operates an installation in which waste is usually used as the main fuel for the purpose of producing heat or electricity, then --  (i) in the case of an installation for producing heat, use other fuel in addition to waste to produce the heat, and (ii) in the case of an installation for producing electricity, use other fuel to assist in burning the waste to produce the electricity, and, in an emergency, use other fuel instead of waste to produce the heat or electricity; and a disposal authority may use, sell or otherwise dispose of any heat [ F77 or electricity ] produced by the authority by virtue of this section. [ F78 (2) Nothing in subsection (1) of this section shall be construed as exempting a disposal authority from the requirements of Part I of the Electricity Act 1989. ] (4) Subsection (6) of section 12 of this Act (except paragraph (b) of that subsection) and subsection (7) of that section (except so