The Bureau of Mines, in cooperation with the National Oceanic and Atmospheric Administration (NOAA), has updated a 1977 NOAA report prepared by Dames & Moore entitled, "description of manganese nodule processing activities for environmental studies." This updated report contains detailed flowsheets and descriptions of the five potential first-generation nodule recovery schemes now considered most likely to be used by industry; they are high-temperature gas reduction and ammoniacal leach, cuprion ammoniacal leach, high- temperature and high-pressure h2so4 leach, reduction and hcl leach, and smelting and h2so4 leach. The first three processes are three- metal recovery schemes (cu, ni, and co) with the option of mn recovery from the tailings. The remaining two processes are four- metal (cu, ni, CO, and mn) recovery schemes. All except the hcl process are assumed to use a nodule feed rate of 3 million tons per year (dry basis). Final metal products are CO powder and cathode cu and ni. A minor amount of ni is also recovered as powder, and some cu and zn are recovered as mixed sulfides. Manganese in the four- metal processes is recovered as either manganese metal or ferromanganese.