Harvesting System Design and Performance - Engineering and Science of Biomass Feedstock Production and Provision - page 108

Fig. 5.25 ( a ) Self-propelled forage harvester chopping Miscanthus. ( b ) A single-pass machine
that can mow and bale in a single pass

Comparedtootherenergygrasses,Miscanthuspresentsthegreatestchallengeto
traditional hay and forage harvesting machinery because of its higher yield and high
stalk rigidity. The thickness and sturdiness of Miscanthus stems make them difficult
to cut and convey. Heavy conditioning after mowing helps to break stems and
improve crop flow into a baler. Metal crimping rollers perform better than the rub-
ber rollers. Poor conditioning causes plugging of baler and frequent field stops.

5.4.1.2 Single-Pass Harvesting of Energy Grasses

A single-pass machine has advantages such as eliminating one pass and reducing ash
content and biomass losses. A forage harvester is a good example of a single-pass
harvesting machine. A forage harvester cuts and conveys the chopped biomass into
an accompanying wagon (see Fig. 5.25a ). The chopped biomass has a typical density
of100kgm −3 comparedto150kgm −3 for a square baler. There have been attempts
to develop a single-pass machine that would cut energy grasses and then bale the
harvested biomass, thus eliminating the need for a second pass (see Fig. 5.25b ).