This study includes the results from 2 experiments. The first experiment consisted of Exp 1a and Exp 1b. Each Exp was a factorial design (2*3) with 3 replications. Factor 1 was the source of crude protein (CP), that being plants. [Exp 1a CP was Operculia turpethum (OT) and Psophocarpus scandens (PS). Exp 1b CP was fish meal (FM) and soybean meal (SM))] Factor 2 was the protein level ranging from 12 to 16 %CP in increments of 2. Exp 2 was a completely randomized design with 4 treatments and 3 replications. The treatments were levels of urea with 12, 14 and 16% CP (DM). The results show that In Exp 1a, CH4 production at 72h of OT (79.6 ml/g DOM) was significantly lower (PDOM), which was the lowest value compared to the others (Pat 72h of FM (71.5 ml/g DOM) was significantly lower (P16%CP treatment (67.1 ml/g DOM), which was the lowest (P(78.0%) was significantly higher (PCH4 production of urea level at 16% CP (56.1 ml/g DOM) was the lowest compared to the others (PCP levels by protein nitrogen or non-protein nitrogen reduced methane production. Key words: plants, crude protein, in vitro greenhouse production, non-protein nitrogen