吳宓蓉 博士

散雜貨碼頭設計顧問專家兼專案經理

---

Sustainability is the key issue currently in the energy sector. To ensure mankind’s future, it is necessary to make use of renewable energy rather than continuing to rely on fossil fuels. There are various types of renewable energy options, such as solar energy and wind energy. However, only biomass can be used for a wide range of applications, for example wood pellets and wood chips (see Figure 1) can be used in co-firing power plants to produce heat and electricity while biodiesel is used in the transport sector.  

Figure 1 Solid biomass fuels (from upper-left hand with counter-clockwise rotation: wood pellets 6mm, torrefied pellets 6mm, wood chips 0-40mm).

Biomass comes in various forms (e.g. wood pellets, biodiesel, biogas) and increasingly it is being traded in international markets. Bradley et al. [1] have indicated that shipping is the main method to transport biomass. In addition, other studies ( [2] [3]) have concluded that the most preferable biomass supply chain is long distance transport via shipping (see Figure 2). This implies that marine terminals in ports will be the important hubs within the logistics chain.

Figure 2  Geographical system outline [2].

Depending on the commodity form, biomass is handled mostly by dry bulk and liquid bulk terminals. From a marine terminal’s point of view, it is essential to understand the material properties in order to handle biomass properly. For a liquid terminal the challenge is easier to tackle as there are many international standards/specifications that regulate liquid biomass products. No major obstacles are to be expected for handling liquid biomass substances.

However, it is a different story for solid biomass fuels. Compared to other commonly handled dry bulk commodities (e.g. coal, soybean), solid biomass fuels have a much wider range of material characteristics. Table 1 shows the comparison of physical properties, relevant for equipment design and handling system selection, between solid biomass fuels, coal, and grain. It shows that up to four times the volume of solid biomass fuels is required for the same energy output compared to coal (see Table 1).

Table 1 Comparison of physical properties relevant for equipment design and handling system selection [4].

Material property	Solid biomass fuels	Coal	Grain
Bulk density (kg/m3)	220 – 650	640 – 920	700 – 870
Moisture content (%)	4 – 49*	15 – 65	5 – 20
Lower heating value (GJ/ton)	8 – 21	30	N/A
Angle of repose (°)	34 – 47	27 – 38	25 – 27
Wall friction angle (°) (Stainless steel)	17 – 30	25 – 35	12 – 14
Effective angle of internal friction (°)	40 – 53	55	29 – 31