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  <xsd:element abstract="true" id="hcci_InventoryTypesAxis" name="InventoryTypesAxis" nillable="true" substitutionGroup="xbrldt:dimensionItem" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="hcci_InventoryTypesDomain" name="InventoryTypesDomain" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="hcci_MachineryVehiclesAndEquipment" name="MachineryVehiclesAndEquipment" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element id="hcci_MachinesInventory" name="MachinesInventory" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element abstract="true" id="hcci_MarketSpreadAxis" name="MarketSpreadAxis" nillable="true" substitutionGroup="xbrldt:dimensionItem" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="hcci_MarketSpreadDomain" name="MarketSpreadDomain" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="hcci_Numberoflocations" name="Numberoflocations" nillable="true" substitutionGroup="xbrli:item" type="xbrli:integerItemType" xbrli:periodType="instant" />
  <xsd:element abstract="true" id="hcci_OilBusinessSegmentMember" name="OilBusinessSegmentMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="hcci_OilInventory" name="OilInventory" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element abstract="true" id="hcci_OptionsOutstandingDomain" name="OptionsOutstandingDomain" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="hcci_OptionsOutstandingStatusAxis" name="OptionsOutstandingStatusAxis" nillable="true" substitutionGroup="xbrldt:dimensionItem" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="hcci_PatentsFormulaeAndLicensesMember" name="PatentsFormulaeAndLicensesMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="hcci_Plantshutdown" name="Plantshutdown" nillable="true" substitutionGroup="xbrli:item" type="us-types:durationStringItemType" xbrli:periodType="duration" />
  <xsd:element id="hcci_ProfitBeforeCorporateSellingGeneralAndAdministrativeExpenses" name="ProfitBeforeCorporateSellingGeneralAndAdministrativeExpenses" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="hcci_RFTIMember" name="RFTIMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="hcci_RTIMember" name="RTIMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="hcci_RepaymentsOfContingentConsideration" name="RepaymentsOfContingentConsideration" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element id="hcci_Rerefinerycapacity" name="Rerefinerycapacity" nillable="true" substitutionGroup="xbrli:item" type="xbrli:integerItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="hcci_SavTechMember" name="SavTechMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="hcci_ScheduleOfIntangibleAssetsTableTextBlock" name="ScheduleOfIntangibleAssetsTableTextBlock" nillable="true" substitutionGroup="xbrli:item" type="nonnum:textBlockItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="hcci_SegmentInformationAbstract" name="SegmentInformationAbstract" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element id="hcci_SellingGeneralAndAdministrativeExpensesDepreciation" name="SellingGeneralAndAdministrativeExpensesDepreciation" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="hcci_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsNonvestedWeightedAverageGrantDateFairValueRollForward" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsNonvestedWeightedAverageGrantDateFairValueRollForward" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element id="hcci_SolventsInventory" name="SolventsInventory" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element abstract="true" id="hcci_StockIssuedDuringPeriodAxis" name="StockIssuedDuringPeriodAxis" nillable="true" substitutionGroup="xbrldt:dimensionItem" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="hcci_StockIssuedDuringPeriodDomain" name="StockIssuedDuringPeriodDomain" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="hcci_SubsequentEventAbstract" name="SubsequentEventAbstract" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="hcci_TermA1LoanMember" name="TermA1LoanMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="hcci_TermALoanMember" name="TermALoanMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="hcci_TotalLeverageRatio" name="TotalLeverageRatio" nillable="true" substitutionGroup="xbrli:item" type="xbrli:pureItemType" xbrli:periodType="duration" />
  <xsd:element id="hcci_TradeReceivablesNet" name="TradeReceivablesNet" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element abstract="true" id="hcci_ULNTRSMember" name="ULNTRSMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="hcci_WorkingCapitalAdjustment" name="WorkingCapitalAdjustment" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:periodType="instant" />
</xsd:schema>


