Transportation - Engineering and Science of Biomass Feedstock Production and Provision - page 155

In research, there is a need for reporting results in a consistent standardized
manner. Apart from the fact that, to date, ample literature in the United States still
uses the archaic English Unit system, there are other areas where inconsistencies
arise. For instance, for size reduction, the specific energy consumption per unit of
resulting particle area (MJ m −2 particle area) should be used for efficiency evalua-
tion rather than the specific energy consumption per unit of mass (MJ kg −1 ). For
energy requirement, it is logical and intuitive to express energy usage of machin-
ery in the PIHV, rather than Joule/tonne or worse, in BTU/lb. In economic studies,
the use of purchase power parity is more sensible than using currencies such as
US$ or Euro.

6.5.3 Interface Between Feedstock Provision and Conversion

Research to date has either focused on the biomass provision chain or bio-conversion
aspects. The schism between the provision and conversion research is understand-
able, since they have traditionally been disconnected by pretreatment. There is an
urgent need for a concerted effort to observe the bioenergy provision and conversion
process in a holistic manner, rather than as individual entities.

6.5.4 Biomass Pretreatment During Storage

Storage of biomass is a liability, but it can also be an asset. The duration of storage
can be long, and during this time, there is an opportunity to expose the biomass to
chemicals for slow pretreatment. The most accessible form of biomass is directly
after size reduction, but this form has a very low density requiring large volumes of
storage. A superior option may be to treat the biomass with a pretreatment agent
between the size reduction and pelletization operations. This concept of pretreat-
ment during storage has had little attention in the literature.

6.5.5 Feedstock Preprocessing

Among the three main operations during biomass provision—harvesting, size
reduction, and compression—size reduction is by far the most energy-intensive. For
instance, size reduction of Miscanthus through a screen with an aperture size of
1 mm requires up to 5 PIHV, whereas woody biomass such as willow [ 20 ] required
12 PIHV. To reduce the energy requirement of size reduction, dedicated milling
machines that employ knives with optimal cutting angles and serrations, potentially
fitted with long-lasting ceramic coatings, operating at a cutting speed that mini-
mizes energy use within an acceptable throughput window, are essential.