Page 334 - Advances in Eco-Fuels for a Sustainable Environment

Thermal depolymerization of biogas digestate 289

C i
U d ¼ (10.6)
m dig:

where,

C i ¼ C AC + C AOC (10.7)
According to Santana et al. [57],

n
ð 1+ iÞ i
C AC ¼ I j n (10.8)
ð 1+ iÞ 1
and

(10.9)
I j ¼ 1:81 E ISBL, j
and according to Sinnott [58],

n
X
(10.10)
E ISBL, j ¼ f L Cost i, j
i
In Eqs. (10.6)–(10.10), C i is the total cost incurred per year; m dig. is the mass of digestate
handled per year, and initially specified to be 5000tons per year; C AC represents the
annual equivalent capital cost in US$; C AC represents the annual operating cost in
US$; n and i represent the project lifetime and the project discount rate, specified to
be 10years and 10% respectively; I j represents the capital cost in year j; E ISBL,j repre-
sents the inside battery limit equipment cost in US$ in year j and serves to incorporate
the cost associated with the utilization of resources for the acquisition, transportation,
and installation of equipment within the processing area [57];and f L represents the Lang
factor, given as 3.60 for mixed fluid-solid processing systems [58].

10.3.1 Cost estimation methods for the proposed HTL-digestate
processing pathway

10.3.1.1 Equipment purchase cost
AnestimateofthepurchasecostoftheHTLreactorwasobtainedusingchemicalengineer-
ing plant cost estimation methods. The HTL reactor cost was estimated as follows [59],

0:5
Cost HTL ¼ 1:5 13, 000 + 34, 000V R (10.11)
where,

_ m dig: t T
V R ¼ (10.12)
ρ dig: