Volume 13: Industry Processes and Controls
6. Rendering
Introduction

6.1 The rendering industry processed the waste from the carcasses of cattle and other farm animals. The process involved crushing the raw material followed by the indirect application of heat. This evaporated the moisture and enabled the fat, known as 'tallow', to be separated from the high-protein solids, known as 'greaves'. In its purest form, tallow is a creamy-white substance. Annex A to this chapter describes how it is further processed. The greaves were pressed, centrifuged or subjected to a process of solvent extraction to remove more tallow, before being ground into meat and bone meal (MBM). ¹ In the 1980s, both tallow and MBM had a good commercial value, although it was the tallow which was the primary product of rendering.

6.2 Slaughterhouses use renderers to fulfil their statutory obligation to dispose of animal by-products within 48 hours of slaughter ² and, before the emergence of BSE, were paid by them for material that might otherwise have been considered useless waste. Epidemiological work carried out in 1988 by Mr John Wilesmith of the CVL suggested that compound animal feed containing infective MBM was the primary mechanism by which BSE spread throughout the UK. Thus the industry plays a central role in the BSE story. Mr Wilesmith subsequently concluded that changes to rendering processes in the early 1980s might have led to the emergence of the disease (see vol. 3: The Early Years, 1986-88).

6.3 It has become a widely held belief that BSE was allowed to emerge as a result of the relaxation by the Government of controls over the rendering process, coupled with a lowering of standards by renderers. The evidence received by the Inquiry does not support either conclusion, as is discussed more fully below.

6.4 This chapter looks first at some of the main features of the industry. It then goes on to describe the various processes in rendering as at 1986, and examines some issues relevant to the role of the industry in the emergence and spread of BSE. Finally it shows how the industry adapted to changes during the period covered by the BSE story, including changes in the handling of the offal designated as Specified Bovine Offal (SBO).