TECHNOLOGY FOCUS - BIOTECHNOLOGY - Preferred Method: In producing methane-utilizing microorganisms in a confined apparatus, the conveyance means includes any means for conveying the methane within the ruminant animal exhalation to the mutual-exposure means. The conveyance means also conveys the ruminant animal exhalation and the methane from the nostrils, mouth, or nostrils and mouth of a ruminant animal to the means of mutual-exposure. The mutual-exposure means comprises any means where the ruminant animal exhalation and the methane therein is conveyed and exposed to the methane-utilizing microorganisms and the growth-culture medium in the microorganism growth apparatus, where the methane-utilizing microorganisms reproduce in or on the growth-culture medium in the apparatus using the methane for growth. It further includes providing a means for causing the methane, the methane-utilizing microorganisms, and the growth-culture medium to be mutually exposed in a batch, semi-batch, or continuous manner. The growth-culture medium comprises any medium promoting the growth of the microorganisms, including any liquid, semi-liquid, gas, particulate, ceramic, foam, plastic, alginate gel, clay, nutrient, or other appropriate growth-culture medium. The microorganisms are either naturally occurring or genetically engineered, where the microorganisms either have or have not been previously exposed in the mutual-exposure means. Preferably, the type of methane-utilizing microorganisms to be used in the confined apparatus is determined by one or more factors selected from amount of growth desired, methane s availability, or nutrient availability. It also comprises providing a means to periodically harvest the product of the microorganism growth, including microorganism biomass, and any other products associated with the growth. It also provides a means to periodically replace and/or renew the growth-culture means. The method further provides a means to situate the means of mutual-exposure entirely on the body of a ruminant animal. It also provides a means to situate the means of conveyance, but not the entire mutual-exposure means, on a ruminant animal. No part of the means of mutual-exposure is situated on a ruminant animal.