30 Introduction to Renewable Biomaterials
Table 1.31Share (%) of cost factors in bio-based production of bulk chemicals
(Kircher, 2014).
Feedstock
Auxiliary
materials Labor Maintenance Energy Depreciation Interest
50 15 15 14 4 1 1
especially cost of feedstock are decisive and can make up to 40–50% of total production
cost (Table 1.30). Compared to fossil feedstock renewable carbon sources still struggle
on a pure cost basis because of expensive (i) harvesting from large areas, (ii) shipping
of bulky materials, (iii) storing of degradable biomass, and (iv) preprocessing. Reducing
feedstock cost will be key in realizing the bio-economy (Table 1.31).
1.4.2 Feedstock Demand Challenges
Not only cost but also the required volume is a topic to discuss. The global consumption
of coal, oil, and gas is about 13 billion tons. When assuming an average carbon content
of about 85% in fossil resources, this means that approximately 11 million tons of fossil
carbon is consumed annually.
To replace fossil carbon by agriculture alone, this sector would need to expand by a
factor of 2.5 from today – 14–36 billion tons of biomass (equivalent to 18 billion tons
of carbon). Even when considering future yield increase by plant breeding, cultivation
methods, and bringing more areas on top yield level, it seems risky to seek the solution
only in more agriculture, as soil erosion, climate change, and fertilizer shortage (e.g.,
geological phosphate resources are running out) raise more uncertainties.
Obviously relying on agriculture alone is not enough. Industries need to exploit new
sustainable carbon sources such as second-generation lignocellulosic raw materials.
They present so-called non-food biomass from agriculture as well as forestry. Such
options as well as processing side streams and third-generation carbon sources like CO
have been discussed earlier. About 0.5–1.4 billion tons of biomass have been estimated
to be sustainably available; a volume obviously not sufficient to replace fossil carbon in
total.
Such a conflict asks for setting priorities: The modern bio-economy should be
focused on products without an alternative to the use of carbon. These are at first
organic chemicals and according to the state-of-the-art heavy-duty fuels such as
aeration fuel. Today, organic chemicals consume about 7% (280 million tons containing
238 million tons of carbon) of the total fossil oil production. This gives the theoretical
minimum volume range to be satisfied by biomass. In fact, the biomass demand will be
significantly bigger as the stoichiometric productivity of bio-based processes is generally
lower than that of chemical synthesis, but this number gives an orientation. Compared
to the biomass volume, which is currently sustainably available (0.5–1.4 billion tons
containing 250–750 billion tons of carbon), it appears appropriate to replace fossil
carbon in chemical synthesis and in addition produce some bio-fuel. Power generation
and short-distance mobility are not really dependent on carbon sources. These markets
may run on solar, wind, geo, thermal, hydro, and more alternative power sources and
the storage media required.
