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Simulator · illustrative

Where does the smell go?

Choose the wind and an emission scenario. The map shows how far the odour of a biogas plant could be noticeable, according to a simple dispersion model checked against field measurements at other plants.

Illustrative simulation based on scientific literature and other countries' rules; it does not replace an odour study of the project. How it is calculated

Based on real data

Real or measured data

  • Guarda wind: hourly climatology (Open-Meteo, ERA5)
  • Distances to homes and villages (MOV.AP measurements on satellite imagery)
  • Odour emission rates of other plants (published studies)

Assumptions, flagged (Assumption)

  • Assumption: The emission scenario chosen (low, medium, high or failure)

How it is calculated (Methodology)

How much would you hear?

Choose how many loads arrive a day, by which route, at what hours and a plant noise scenario. The map shows the plant's noise contours and the trucks on the two routes; the tables compare them with the background noise, Portuguese law and the WHO guidelines.

Illustrative simulation based on studies of other plants, Portuguese law and WHO guidelines; it does not replace a noise study for the project. How it is calculated

Based on real data

Real or measured data

  • Road routes (OpenStreetMap)
  • Distances (MOV.AP measurements on satellite imagery)
  • Guarda wind climatology (ERA5)
  • Noise of comparable plants and trucks (published studies)
  • Portuguese legal limits (General Noise Regulation)
  • WHO road-traffic noise guideline values

Assumptions, flagged (Assumption)

  • Assumption: 25 loads a day (capacity not disclosed)
  • Assumption: Typical rural background noise (28–35 dB(A)), not measured in the villages
  • Assumption: Split of trips between the two routes (50-50)
  • Assumption: Truck working hours
  • Assumption: Plant noise scenario (low, central, high)
  • Assumption: Façade distance of 5 m
  • Assumption: Truck speed (30 km/h in villages, 60 km/h outside)
  • Assumption: Unloading time (45 min)

How it is calculated (Methodology)

The interactive simulator needs JavaScript. The scenarios, sources and validation note are on this page.

Hourly mean concentration at ground level

  • 1 ouE/m³ odour possibly noticeable
  • 3 ouE/m³ odour probably noticeable
  • 5 ouE/m³ distinct odour / possible nuisance

Display capped at 3 km

Continuous plant noise at ground level

  • 35 dB(A)
  • 40 dB(A)
  • 45 dB(A)

35 dB(A): typical rural background noise by day. 45 dB(A): with ambient noise up to this value, the RGR does not apply the annoyance criterion.

Trucks on the routes

Simulated time --:--

    area where each truck is ≥10 dB above the background noise (assumption: the 10 dB margin is a modelling choice)

    Typical conditions: prevailing west-north-westerly wind, 3 m/s, overcast sky

    Emission scenario

    Wind direction (where it blows from)

    Drag the pointer or use the arrow keys (16 points); Shift + arrow moves 1°.

    3 m/s
    Time of day
    Cloud

    25 loads = 50 passages (there and back)

    Capacity and truck numbers not disclosed: we use 25 loads a day (50 passages, there and back), a conservative figure, probably on the low side.

    Split between the routes (Assumption)
    Truck hours (Assumption)

    The hours have not been disclosed. “Daytime only” is the RGR day period; “also at night” spreads the loads over 24 hours.

    Plant noise (sound power LwA) (Assumption)

    estimate from components (low confidence). There are no public data on this plant's noise: the value is estimated from the equipment of comparable plants.

    Wind

    Indicative only: the noise contours are not adjusted for wind, because the research found no defensible value for that correction.

    Scenario source: 20,000 ouE/s

    Villages, farms and water points

    Distance from the estimated centre of the project; modelled hourly mean concentration.

      Homes and villages: plant noise

      Predicted continuous level from the plant, compared with the background noise of each period. The distance is MOV.AP's measurement from the parcel boundary: the worst case, with the equipment at the point of the parcel nearest each home; the contours on the map start from the parcel centre. The RGR comparison adds a +3 dB tonal penalty; the difference from the background does not include it.

        Villages the trucks drive through

        Each load comes in and goes out by the same route: two passages through the village.

          What the law says

          The RGR annoyance criterion (+5 dB by day, +4 in the evening, +3 at night above the residual noise) does not apply when outdoor ambient noise is ≤ 45 dB(A) (art. 13(5)). In quiet villages, this rule likely does not protect residents.

          Zone: mixed zone (1st revision of the Guarda PDM, art. 34; entry into force not confirmed), with limits Lden 65 / Ln 55 dB(A). The homes have no classification of their own: this is an assumption.

          WHO guidelines

          Road traffic noise: Lden 53 dB and Lnight 45 dB. Indications, not legal findings.

          Model

          Plant: a point source with simplified ISO 9613-2 propagation (spreading, air absorption of 2 dB/km and ground effect).

          Assumed mean source/receiver height (1.5 m)

          Trucks: maximum level of each pass at 7.5 m (75 / 82 / 88 dB(A); we use the central value), reduced to the house front plus +3 dB for reflection; the daily level adds up the energy of all passes.

          30 km/h in the village: assumption (07 §9.2)

          How it is calculated

          Validation

          With 20,000 ouE/s and daytime conditions the model gives 300–800 m; field measurements at European biogas plants: 250–600 m.

          Model

          Steady-state Gaussian plume, ground-level source spread over ~5 ha, ground reflection, Briggs (rural) dispersion.

          How it is calculated

          Thresholds

          • 1 ouE/m³ — odour possibly noticeable
          • 3 ouE/m³ — odour probably noticeable
          • 5 ouE/m³ — distinct odour / possible nuisance

          Sources on this page

          1. Climatologia do vento no local, 2021–2025: reanálise ERA5 através da Open-Meteo Historical Weather API (16 setores, velocidade, dia/noite) Open-Meteo.com (dados ERA5 do Copernicus/ECMWF) · período 2021–2025, calculado em 16.10.2026
          2. MOV.AP: medições sobre imagem de satélite, outubro de 2026 (distâncias do limite da parcela à zona de exploração de água, quintas e aldeias) MOV.AP · 16 Oct 2026
          3. Odour impact assessment, Bio Agrigas (Mullingar): Odour Monitoring Ireland report 2011A148(1) Environmental Protection Agency (Irlanda), processo de licença · 2011 (ficheiro da EPA exportado em 01.08.2012)
          4. Odour emissions impact of on-farm biogas production with co-digestion: a case study in four European farms Université de Liège (Adam G. et al.), conferência ManuREsource, Bruges · 5 Dec 2013
          5. Bayle et al. (2018), Chemical Engineering Transactions, vol. 68, pp. 79–84: emissões de odor em três unidades de metanização em França Chemical Engineering Transactions (AIDIC) · 2018
          6. Rotas rodoviárias entre o local e as aldeias: extração Overpass, 17.10.2026 © OpenStreetMap contributors (licença ODbL) · 2026-10-17
          7. REC: Noise Impact Assessment, Coursers Farm AD (AC100899-1R3) REC (consultora, para o requerente) · 2016-05-31
          8. Decreto-Lei n.º 9/2007: Regulamento Geral do Ruído (art. 3, 11 e 13, anexo I) Diário da República
          9. Environmental Noise Guidelines for the European Region (2018): tráfego rodoviário, Lden 53 dB e Lnight 45 dB Organização Mundial da Saúde, Gabinete Regional para a Europa · 2018
          10. Guidance on the assessment of odour for planning, version 1.1 Institute of Air Quality Management (Reino Unido) · julho de 2018
          11. Arrêté du 12 août 2010 relatif aux prescriptions générales applicables aux installations classées de méthanisation relevant du régime de l'enregistrement (rubrique 2781), version consolidée AIDA (INERIS), Ministère de la Transition écologique · 12 Aug 2010
          12. Redmore Environmental: Noise Impact Assessment, Rufford AD (ref. 1288-2) Redmore Environmental · 2017-04-20
          13. ISO 9613-2: atenuação do som na propagação ao ar livre (método simplificado) Organização Internacional de Normalização
          14. EPA Irlanda: documento de licença com ruído de fundo rural noturno (LA90 30–31 dB(A)) Environmental Protection Agency (Irlanda)
          15. Aviso n.º 30765/2025/2: 1.ª Revisão do PDM da Guarda, art. 34 (zonamento acústico) Diário da República, 2.ª série, n.º 243 · 2025-12-18
          16. Regulamento (UE) n.º 540/2014, anexo III: limites de ruído de veículos (N3, medição a 7,5 m) União Europeia (cópia legislation.gov.uk)
          17. FHWA: níveis de ruído de passagem de camiões pesados (Lmax a 50 pés) Federal Highway Administration (EUA)
          18. Die Entwicklung des Ausbreitungsmodells AUSTAL2000G (Berichte zur Umweltphysik 5, 2.ª edição) Janicke L. e Janicke U., Ingenieurbüro Janicke · março de 2007
          19. Ata da reunião ordinária da Câmara Municipal da Guarda de 19 de junho de 2026 (Ponto 18, Proposta VPCM n.º 10/2026) Câmara Municipal da Guarda · 19 Jun 2026
          20. Odour Impact by Field Inspections: Method and Results from an Agricultural Biogas Facility Keck M. et al. (Agroscope), Chemical Engineering Transactions, vol. 40 · 2014
          21. ALOHA (Areal Locations of Hazardous Atmospheres) 5.4.4 Technical Documentation, NOAA Technical Memorandum NOS OR&R 43 NOAA (Estados Unidos) · 2013

          See all sources