The first TGER prototype (Fig. 3) was built as a part of a Phase IISTTR (Small busi­ness Technology Transfer Research) program and demonstrated proof of principle,

Fig. 4 TGER after retrofit

but was not rugged enough to deploy to an OCONUS (outside the continental United States) site for field testing and validation. The initial function of the follow-on effort was to upgrade the existing prototype with better, more advanced equip­ment that could withstand the stresses of a three month OCONUS deployment in an operationally harsh environment (Fig. 4).

Three of the key improvements identified during testing of the Phase II TGER and applied during the retrofit and fabrication are highlighted below.

(1) First stage materials preparation (Industrial shredder and separations system). This component combines several key tasks which currently are done on the original prototype with separately acquired and integrated third-party compo­nents. Tasks include shredding, rinsing, auguring and compacting bioreactor residuals. The Industrial shredder performs these functions as a single com­ponent with half of the electrical power required by the original TGER. The new Industrial shredder was retrofitted onto the original prototype and included during fabrication of the second prototype.

(2) Second stage pelletizer. Testing demonstrated that the size and shape of the pel­lets were the most critical qualities of gasifier feed-stock, followed by pellet density and then proportions of waste content (plastic vs. cellulosic, other). Our original view of the feedstock had focused on the latter, i. e. waste content pro­portions, and had used a less expensive compaction channel for gasifier pellets. Subsequent off-line testing with pellets made with equipment demonstrated a marked improvement in gasifier performance and subsequent engine output. The pelletizer, shown in Fig. 5, was included in the second TGER design and was a retrofitted improvement to the original prototype.

(3) Stainless steel commercial grade distilling column. The stainless steel distilling column was upgraded from standard steel to stainless to prevent the introduction of rust into the distilling apparatus [9].