Terra has environmental management systems auditors, certified by IRCA, experienced from 2001 (certification and follow-up ISO 14001, internal, coorporate, legal compliance).
The main companies have audited are:
| SA MIRAT | Manufacture of fertilizers |
| NOVOTECNI | Civil engineering |
| EFFEM SPAIN | Manufacture of food for pets |
| Transportes Gutierrez | Road transport |
| Iberhidra | Civil engineering |
| Vodafone Spain | Communications |
| Proting sl | Civil engineering |
| Hervatrans sl | Road Transport |
| Transportes chapin sl | Road Transport |
| Urdecom buildings S.A.. | Civil building |
| Segura de automoción S.L.. | Wholesale. Repair of motor vehicles |
| Clinica triana s.l. | Medical services |
| Gea Medioambiente | Management of polluted soils, hydrologic studies |
| Consulting engineers ALATEC GROUP | Civil engineering |
| Grupo JCDecaux | Communication |
| DETERIN SA | Manufacture of chemistry products |
| Tecnicas en Plagas S.L.. | Plague control |
| Basademar | Aquaculture |
| Transportes ESK | Transport Activities |
| Disval S.A. | General construction of buildings and civil engineering works |
| OTR oficina técnica de resinas | Manufacture of chemical products |
| Piscufactoria Aguadulce (Culmarex group) | Aquaculture |
| GEOcontrol | General construction of buildings and civil engineering works |
| Información y Control de la Planificación | Cargo Handling, Storage and Supporting Transport Activities |
| Eurimar S.L. | General construction of buildings and civil engineering works |
| Centro Informático Pozuelo | Hardware maintenance |
| Grupo CAT Peninsula | Cargo Handling, Storage and Supporting Transport Activities |
| Cartonajes MIMO | Manufacture of paper |
| Indoor Air Quality | Cleaning and disinfections of air conditioners |
| NOVOTECNI | Civil engineering |
| Torrecilla Urueña Consultores | Civil engineering |
| Transportes Santos S.A. | Transport Activities |
| Gedemasa | Food retails |
| Grupo Python | Printing |
| Limpiezas Moratinos | Cleaning |
| Ecoplag | Plague control |
| Coserfo S.L. | Forestry and logging related service activities |
| ABB Power Technology | Manufacture of electrical equipment |
| Tomates de Miajadas | Processing and manufacture of fruit and vegetables |
| Martin y Cuadrado | Construction, sewage water treatment plants |
| Boart Longyear | Basic Metal Products and Fabricated parts for drilling |
| Tolsa | Manufacture of non-refractory ceramic goods |
| Equisat CLM SL | Transport of hazardous waste |
| OTR oficina técnica de resinas | Drilling for groundwater |
| Perforaciones Ibéricas SA | General construction of buildings |
| Castilla de construcciones ABS | Civil engineering |
| Talleres Barga | Installation of electrical wiring and fittings |
| DIODE | Manufacture of computers |
| Naviera Sicar SL | Sea charter management |
| NOVOTECNI | Engineering and landscape management |
| CONTSE SA | Manufacture of medical gases |
| Guaguas Municipales Gran Canaria SA | passenger land transport |
| TRN | Engineering |
| Moviltech TECHNICAL SERVICE SL | Manufacture of electric domestic appliances |
| PID ENG&TECH SL | Manufacture of laboratory equipment |
| OTR oficina técnica de resinas | Manufacture of chemical products |
| Sereng y Mantei SA | Maintenance of vending machines |
| Servi Hogar Extremeña | Maintenance and cleaning of buildings |
| NOVOTECNI | Civil engineering |
| Colegio Ramon y Cajal | Education |
| Hormigones y Obras Parros | Civil engineering |
| SCP y Márketing Espectacular | Publicity |
| Heymo Ingenieria S.A.. | Civil engineering |
| Jardinería Garcia Lorca | Gardening. |
| Drizoro | Manufacture of Concrete, cement, lime, plaster etc. |
| Trafosan Medio Ambiernte | Forestry works |
| Consultoria e Ingeniería de Ensayos y Sistemas | Civil engineering |
| Servauto Centromotor S.A. | Wholesale. Repair of motor vehicles |
| Sercaman 1 | Computer repairs |
| OTR oficina técnica de resinas | Manufacture of chemical products |
| Viveros Bárboles | Forestry works |
| Ginprosa Ingenieria SL | Civil engineering |
| Industria Metalurgica SA Branas | Metal structures |
| Plastal Spain SA | Plastic components for the car industry |
| Servauto Centromotor SA | Wholesale. Repair of motor vehicles |
| Revesa SA | Wholesale. Repair of motor vehicles |
| Molducea SA | Construction of modular buildings |
| Grupo AMS (Madrid) | Electrical assembly. Civil engineering |
| Granja Cinegética de Aves S.L.. Coto Valdobra | Game reserve, Skeet shooting, restaurant, paintball, sports and dog’s home. |
| Bombardier Transportation. Malaga-Albobendas-Entrevias | Maintenance of high speed trains |
| AMO Abbott laboratories | Medical laboratories. Manufacturing of ophthalmologic products. |
| Trapaga Bombardier Transportation | Manufacture of electric rolling stock applications |
| Abbott Granada | Medical laboratories. Manufacturing of nutrition products |
| Bombardier Transportation. human | Maintenance of short distance trains |
| Albemarle – Chemetall | Chemical treatment of metal surface |
| Acuidoro S.L. | Aquaculture |
| General company Canteras S.A. (Italcementy Group) | Quarrying |
| Bodegas Luis Megía S.L.. | Wine making. Manufacture of beverages |