The First Zero-Impact Olive Mill to Produce Energy

Harvest just started in Italy and while olive mills are work­ing almost at full capac­ity we met the cre­ator of an inno­v­a­tive method of pro­duc­tion that not only has zero envi­ron­men­tal impact but also pro­duces elec­tric and ther­mal energy.

“This sys­tem has reached the high­est level of inno­va­tion for the dis­posal of waste­water,” said Giovanni Cassese, who gained expe­ri­ence in the fam­ily mill at Villa Castelli, in the province of Brindisi, in Apulia. ​“A very sim­ple agri-food process became a zero-impact prac­tice to pro­duce high-qual­ity extra vir­gin olive oil and gen­er­ate power.”

Cassese con­ceived adjust­ments to the mode of oper­a­tion of a mill and sub­mit­ted them to the milling tech­nol­ogy com­pany Pieralisi, which imple­mented the new setup in a plant that can be con­sid­ered the first com­pletely envi­ron­men­tally sus­tain­able olive mill.

“As we know, even the most inno­v­a­tive three-phase sys­tem involves a water con­sump­tion that ranges from 70 to 110 per­cent, while the two-phase sys­tem gen­er­ates very reduced water con­sump­tion but the waste needs to be fur­ther processed to be reusable in some way or digested,” he explained. ​“After extrac­tion with our mill which employs the DMF (multi-func­tional decanter) tech­nol­ogy, we obtain extra vir­gin olive oil and two byprod­ucts or, as I call them, ​‘dif­fer­en­ti­ated pro­duc­tions’ — the vir­gin olive pomace with humid­ity con­tent around 55 per­cent, that is very well suited to the extrac­tion of olive pit, and the olive pâté.”
See Also:A Centrifugal Force: Gennaro Pieralisi
He pointed out that the real inno­va­tion is the use of this prod­uct in a plant for anaer­o­bic diges­tion in the same site of the mill that ​“allows to exploit all the resul­tants of a high-effi­ciency cogen­er­a­tion.”

The olive pâté is a cream that com­pared the de-stoned olive pomace has no lignin and a rel­a­tively high con­tent of polyphe­nols. These two qual­i­ties make it suit­able to be stored for a long period, with­out caus­ing odor, and it is sub­se­quently digested. The result of diges­tion, in a plant adapted to work mate­r­ial with rel­a­tively high solid sub­stance (EUCOmpact tech­nol­ogy), is bio­gas of 60 per­cent methane with a con­sid­er­able aver­age yield of about 150 cubic meters per ton of olive pâté.

“We con­sume 200,000 kilo­watts per year to pro­duce the olive pâté and for all the util­i­ties,” Cassese explained. ​“Since the result of cogen­er­a­tion is 765,000 kW, after sub­tract­ing the mill con­sump­tion and the self-con­sump­tion of the plant, we pro­vide to the power grid an amount of elec­tric­ity to cover the annual needs of more than 50 fam­i­lies.” He clar­i­fied that the cal­cu­la­tion refers to house­holds con­sum­ing over 10,000 kWh/year, but esti­mat­ing the aver­age con­sump­tion of Italian fam­i­lies, he can serve more than 100 fam­i­lies.

Moreover, since the pro­duc­tion of energy oper­ates in cogen­er­a­tion mode, the plant also pro­vides about 800,000kWh of ther­mal energy in the form of heat that can be used within the mill, to help the pro­cess­ing and to main­tain the con­stant tem­per­a­ture of stor­age rooms dur­ing win­ter. While in the sum­mer, thanks to the phys­i­cal prin­ci­ple of tri­gen­er­a­tion, the result­ing heat is trans­formed through a lithium bro­mide absorber into cold water that cools the stor­age rooms.

The result of diges­tion is the diges­tate, that is a for­mi­da­ble fer­til­izer ​“ready to return to the same olive trees that gave us their olives and which in their life­time fixed the CO2 that we re-insert into the atmos­phere through the com­bus­tion of bio­gas.”

This new sys­tem pro­vides con­sid­er­able sav­ings. The bio­gas plant built in the imme­di­ate vicin­ity of the mill allows the reset­ting of trans­port costs of the pâté that is pre­served with­out loss of yield and, given the high amount of digestible dry mat­ter, has a decline in weight after diges­tion of around 20 – 25 per­cent. Moreover, the spread­ing can be car­ried out all year at the farmer’s choice accord­ing to the fer­til­iza­tion plan, and it is no longer nec­es­sary to dis­pose of waste­water in the same peri­ods of pro­cess­ing and har­vest, result­ing in sav­ings of 25 per­cent for trans­port costs.

The use of olive pâté from the DMF tech­nol­ogy gen­er­ates imme­di­ate sav­ings in the man­age­ment expen­di­tures of the mill, with zero con­sump­tion of drink­ing water that would be used to dilute the olive paste in the decanter, the reduc­tion of energy con­sump­tion and the total absence of waste­water result­ing from oil extrac­tion.

According to Cassese, ​“this is at the moment the best extrac­tion sys­tem with regard to water and energy con­ser­va­tion, and envi­ron­men­tal pro­tec­tion.”