An integrated approach to energy use: the case study of the ACEA site

Currently, ACEA utilises biogas obtained from the treatment of the organic fraction of municipal solid waste for thermal and electric energy recovery through endothermic engines (3 MW, in total). By 2020, the biogas produced at the site will no longer be used as a fuel for the combined heat and power units, but it is expected to feed a purification system in order to obtain a flow of biomethane to be injected into the natural gas network. This is part of the Italian strategy to achieve the Horizon 2020 European targets aimed at promoting the renewable production of transport fuels. In order to encourage sustainability and innovative prototype technologies, ACEA has also been involved in some European research projects, in particular for the conversion of biogas into other energy carriers. furthermore, ACEA ha recently built a flexible experimental platform that can used for the validation step of prototypes in an industrial field.


ACEA integrated waste treatment district
ACEA Pierese Idustriae SpA (r sipy ACEA) is a der utiutiity cpay cated i rther Itay which currety prvides services fr uicipaities private cpaies ad cities esurig sustaiabe devepet i three ai areas water eergy ad eviret re specificay the preise specificay dedicated t the evireta sectr is caed itegrated waste treatet district" sice it ecpasses fur waste treatets pats (e wastewater (WW) treatet pat e adfi e cpstig pat ad e aaerbic digesti (AD) pat) highy itercected accrdig t which the waste strea fr e ay bece the iet strea fr ather faciity Furtherre a the iquid effuets geerated at the site fr the cpstig pat the aaerbic digester pat ad the adfi are set t the WW treatet pat The digestate cig fr the aaerbic prcess is set t the cpstig pat where it is used as a startig ateria fr cpst prducti ad the sudge derivig fr the WW treatet pat Fiay a the bigas prduced at the WW treatet pat at the adfi ad at AD pat is cveyed ad tepray stred i the gashder fr the prducti f reewabe eectricity ad heat by eas f cbied heat ad pwer (CHP) uits expitig bigas cbusti The site is a itercected pat fr the aageet f water sudgedigestate ad fr eergy recvery (bth thera ad eectrica) The site is as a exape f the itegrati f the aaerbicaerbic treatet f the rgaic fracti f sid urba waste I fact ACEA utiises the digestate fr the aaerbic digesti tgether with gree residue fr separated urba cecti fr the prducti f highquaity cpst registered uder the FRAWIVA brad which has achieved a quaity certificati by the CIC (Csri Itaia Cpstatri) i 2005 The eectricity ad heat surpus that is t utiised fr itera csupti is sd t the grid i fact ACEA has reaised a wide district heatig etwr servig a user basi f 30000 ihabitats ad a shppig cetre with a actua sie f 76 W t be earged i cig years The curret ai cre f the site is the cbusti f bigas t prduce heat ad eectricity fr CHP uits hwever by 2020 a the bigas prduced at the site is expected t feed a purificati uit fr the prducti f biethae t be iected it the gas atura grid (up t 800 S3h f biethae prduced) fr eargig the uit aready preset i the site which currety prduces biethae fr trasprt fue (up t 50 S 3 h f biethae prduced) This sigificat chage fr the ACEA perspective is aiged t the Reewabe Eergy Directive 200928EC 1 sice the Eurpea Ui has sigificaty supprted the picies aied at the prducti f bifues icudig iquid r gaseus fues such as bidiese ad biethae prduced fr biass These bifues are a reewabe aterative t fssi fues i the EU trasprt sectr strategicay sigificat fr reducig greehuse gas eissis ad iprvig the security f the EU suppy By 2020 Itay i ie with Eurpea picies ais t esure that 10% f trasprt fue ces fr reewabe surces such as bifues At the ACEA site the cversi fr bigas t biethae cud be cuped with the use f atura gas fr the grid (istead f the curret use f bigas) fr feedig the CHP uits i rder t ctiue t esure the eergy eeds bth eectrica ad thera f the pat 2 Energy production at ACEA premises ACEA is respsibe fr the rgaic fracti f uicipa sid waste (FSW) cecti appied directy fr 150000 ihabitats ivig i 47 uicipaities i the suth west f Turi cse t the Frech brder The treatet f the FSW ivves the aaerbic digesti prcess sice this prcess is widey csidered as a effective waste biass treatet apprach 2 Currety the bigas pat treatet serves rughy 1 ii ihabitats aagig 60000 t y 1 f FSW (90000 t y 1 f FSW i the shrt ter) which uderges tw aaerbic digesters characterised by a tta wrig vue f 5000  3  The prcess is therphiic (55 C  1) with a reteti tie f 14 days ad a rgaic adig rate higher tha 6 gTS  3 d 1  Every year re tha 4000000  3 f bigas with a average ethae ctet f 55% vv ad a carific heat f arud 54 Wh  3  are prduced ad used fr esurig heat ad eectricity t the site itsef ad the surrudig area

Thermal use of energy
The thera eergy ca be epyed fr severa uses heatig up the feretative brth fr the AD prcess at 55 C (5070 Why) fr the WW treatet pat (1400 Why) fr the buidig uses (1170 Why) ad fr district heatig (6380 Why) (data is fr 2017) The thera eergy ca be suppied by bth the cbusti bigas i the fr f reewabe eergy (3710 Why) ad by a extera surce (10310 Why) utiisig atura gas fr the grid I fact ACEA expits tw superheated water biers fueed with atura gas fr thera eergy prducti The use f thera eergy is stricty cected t the seas f the year as ca be see i Figure 1 (fr Apri t Septeber) ad Figure 2 (fr ctber t arch) Durig the witer seas the heat prduced is aiy used fr district heatig reachig arud 430 Whh at 800 a Fr Apri t Septeber district heatig requires  re tha 85 Whh ad the ai csupti is acated t the AD prcess It ca be ted that the axiu csupti f thera eergy is ess tha 300 Whh durig the suer seas ad re tha dube that durig the witer seas sice a higher aut f heat is ecessary fr the district heatig ad t a ess extet t aitai the prper feretati teperature at 55 C Figure 3 shws the aua prducti ad dead f eectric eergy as highightig the aut acquired fr the extera surce ad the quatity sd t the grid (data is fr 2017) The reewabe eectric eergy at the ACEA site is prvided by three CHP uits fr bigas cbusti (13700 Why) ad 630 phtvtaic paes (130 Why) hwever there is a ctributi fr the etwr (690 Why) t cpesate fr the ac f eectricity due t the aiteace f the egies breadws r ac f bigas i case f great dead Furtherre 927% f tta aut f eergy csued withi the site was reewabe ad btaied fr bigas cbusti ad phtvtaic paes whie the reaiig 73% was purchased fr the etwr Fig. 1. Uses of thermal energy during the day, from April to September. Thermal energy is employed for district heating, for the wastewater treatment plant, for building uses and for the AD process. Data is for 2017.

Fig. 2.
Uses of thermal energy during the day, from October to March. Thermal energy is employed for district heating, for the wastewater treatment plant, for building uses and for the AD process. Data is for 2017. Fig. 3. Uses of electric energy during (2017). Electric energy derives from biogas combustion (CHP units), from photovoltaic production and from natural gas purchased from the network. The electric production can be used internally or sold to the network.
In addition, 66% of the electricity energy is selfconsumed, and the remaining 34% is sold to the network. The net balance between the electricity purchased and sold to the network is then favourable towards transfer to the national network (+3.9 GWh/y), demonstrating that the amount of electricity sold to the grid (4,590 MWh/y) is definitely greater than that purchased from the external source (natural gas for super-heated water boilers).

Energy production at ACEA premises
Within the EU Framework Program Horizon 2020, ACEA experiments with new technologies for the realisation of innovative prototypes to make renewable energy production as efficient as possible. Among the others, in this concept, there are two projects worthy of note, PROGEO and BIORURPLUS (funded by others; in this concept, there are two projects worthy of note, PROGEO and BIOROBURPLUS. PROGEO (funded by the EU Framework Program Horizon 2020 H2020-EU.3.3, H2020-EU.2.3.1.) is focused on the conversion of CO2 (gaseous effluent from biomethane upgrading) and H2 (from water electrolysis) into bio-methane through a methanation reactor by means of Sabatier reaction, for ensuring the chemical storage of renewable energy [3]. All the biogas produced by AD may be theoretically converted into biomethane to be fed into the grid. In fact, methane is a well-known and widely used fuel and all technologies related to methane storage and distribution are fully available, and ACEA has its own infrastructure to inject it into the grid. Since the hydrogen production from water electrolysis is very demanding of energy, this process is sustainable only when it is possible to utilise low-price electricity (during the night) and the off-peak periods of electricity production. This will be part of the scope of the demonstration project and the ACEA site is expected to perform a demonstration of the 500 kW PROGEO modular unit in order to achieve the final technology readiness levels (TRL) of 8.
BIOROBURPLUS involves the development of a direct biogas oxidative steam reformer for the production of bio-hydrogen to be utilised as inlet streams for fuel cell devices. In fact, BIOROBURPLUS (funded by the EU Framework Program Horizon 2020 -JTI-FCH-2016-1) claims to develop an entire pre-commercial fuel processor delivering 50 Nm3/h (107 kg/d) of 99.9% hydrogen from different biogas types (landfill gas, anaerobic digestion of organic wastes, anaerobic digestion of wastewater-treatment sludge) in a costeffective manner. A dedicated TRL6 demo campaign (>4400 h) will be carried out in the last six months of the project at ACEA premises for the production and purification of bio-hydrogen.
For both cases, ACEA represents the ideal industrial site to validate results obtained from intensive research work, and to assess the production cost and market price of renewable products, in order to be competitive with the traditional market.

Conclusion
Fr the begiig the cpay prpsed a ew de f devepet where waste is csidered as a resurce ad a ew busiess de abe t iprve ad ffer ivative sutis rted i the surrudig area fr evireta ad scia sustaiabiity The ACEA site is currety ivved i a adaptati t the st der ad ivative techgies i ie with the ew evireta requireets estabished by the Eurpea directives  eergy ad eissis The gig activities icude the cpete cversi fr bigas t biethae prducti ad i parae a icrease i the thera recvery fr the CHP ad the tta cversi f the CHP fr bigas t atura gas Fr this perspective atteti is  the ai f prducig y the eectric eergy stricty ecessary fr the itera csupti f the itegrated waste treatet district The ga f the ptiisati prcess is icreasig the efficiet use f eergy withi the sige idustria prcesses