Efficient bio-ethanol production from napiegrass (Pennisetum purpureum Schumach) was investigated. A low-moisture anhydrous ammonia (LMAA)-pretreated napiegrass was subjected to simultaneous saccharification and co-fermentation (SSCF), which was performed at 36°C using Escherichia coli KO11, Saccharomyces cerevisiae, cellulase, and xylanase. It was found that use of xylanase as well as the LMAA-pretreatment was effective for the SSCF. After the SSCF for 96 h, the ethanol yield reached 74% of the theoretical yield based on the glucan (397 mg g-1) and xylan (214 mg g-1) occurring in dry powdered LMAA-pretreated napiergrass.

Napiergrass (Pennisetum purpureumSchumach), a C₄tropical species, has been used for forage since it has high dry matter productivity, sustainability over several years in low-altitudinal sites of Kyushu, and little damage from serious pests. Recently, this grass has gained attention due to its potential as a bioethanol feedstock and for phytoremediation. Napiergrass cultivar Wruk Wona was grown as an annual crop in cadmium- (Cd-) contaminated soils under two cutting frequencies. Annual dry matter yield was not affected significantly by cutting frequency, but the concentration and uptake of Cd were higher when cut twice rather than only once, due to high Cd content of the herbage from the second cutting. Therefore, the soil Cd concentration was reduced by 4.6% when managed by cutting twice in a single year of Napiergrass cultivation.

The effects of two levels of manure application (184 and 275 kg N ha⁻¹ year⁻¹) on herbage yield, quality, and wintering ability during the cropping of a dwarf genotype of late-heading (DL) Napiergrass (Pennisetum purpureum Schumach) oversown with Italian ryegrass (IR; Lolium multiflorum Lam.) were examined and compared with chemical fertilizer application (234 kg N ha⁻¹ year⁻¹) for 4 years to determine a sustainable and environmentally harmonized herbage production in a hilly area (340 m above sea level). No significant (p > 0.05) differences in growth attributes of plant height, tiller density, percentage of leaf blade, or dry matter yield appeared in either DL Napiergrass or IR among moderate levels (184–275 kg N ha⁻¹ year⁻¹) of manure and chemical fertilizer treatments. IR exhibited no significant detrimental effect on spring regrowth of DL Napiergrass, which showed a high wintering ability in all treatments. In vitro dry matter digestibility of DL Napiergrass tended to increase with increasing manure application, especially at the first defoliation in the first three years. Manure application improved soil chemical properties and total nitrogen and carbon content. The results suggested that the lower rate of manure application of 184 kg nitrogen ha⁻¹ year⁻¹ would be suitable, which would be a good substitute for chemical fertilizer application with an equilibrium nitrogen budget for sustainable DL Napiergrass and IR cropping in the hilly region of southern Kyushu.

Ethanol and pentose were produced from lignocellulosic napiergrass by the simultaneous saccharification and fermentation process (SSF) using hydrolytic enzyme and S. Cerevisiae. After the ethanol was removed, the pentose solution was subjected to photocatalytic hydrogen evolution with Pt-loaded TiO₂ under UV-irradiation. This process converted 100 g of napiergrass into 12.3 g of ethanol and 1.76 g of hydrogen whose total combustion energy of (∆H) was 615 kJ. This was close to the ∆H (639 kJ) of the pentose (13.6 g) and hexose (27.4 g) obtained by the cellulose-saccharification of 100 g of napiergrass.

A triple cropping system, combining spring maize, pearl millet, and twice-cut blast disease resistant Italian ryegrass, was examined for the 2016–2017 and 2017–2018 growing seasons to achieve quality herbage production in Miyazaki, southern Kyushu, Japan. The growth of the three crops reached to harvest, even though typhoon and heavy rainfall occurred. Annual dry matter (DM) yield of the triple crops was 4098 g m⁻² and 4349 g m⁻² in the first and second cropping seasons, respectively. The observed total digestible nutrients (TDN) were higher in spring maize (up to 68.2% and 76.8%), pearl millet (up to 60.0% and 67.9%), and Italian ryegrass (up to 71.6% and 68.6%), during the first and second season, respectively, leading to an annual TDN yield of 2357 g m⁻² and 2938 g m⁻². The results suggest that the present established triple cropping system is feasible for obtaining high yields with more digestible nutrients in the forages.

We investigated a new method for the establishment of dwarf Napiergrass by covering stem cuttings with soil in the winter season analogously to summer establishment in sugarcane. Three experiments were conducted, including measuring the labor involved in plant establishment, and an extension study was applied to livestock producers’ fields in two locations. Using this technique, we obtained an emerged plant density of over two plants/m². Moreover, this proved a simple and labor-saving method compared with manual or mechanical transplanting. Sowing of Italian ryegrass at the same time as covering cuttings of dwarf Napiergrass with soil could control spring weed growth without disturbing the emergence of dwarf Napiergrass, suggesting the feasibility of a double-cropping forage production system in the region.