def plant_type_to_fuel(plant_type, construction_year=None):
    """
    Function which infers fuel type from plant plant_type.
    :return: String detailing fuel type
    """
    if plant_type == 'CCGT':
        return 'Gas'
    elif plant_type == 'Recip_gas':
        return 'Gas'
    elif plant_type == 'Meat':
        return 'Meat'
    elif plant_type == 'Wind (offshore)':
        return None
    elif plant_type == 'Offshore':
        return None
    elif plant_type == 'Biomass_poultry_litter':
        return 'Poultry_litter'
    elif plant_type == 'Biomass_meat':
        return 'Meat'
    elif plant_type == 'Biomass_straw':
        return 'Straw'
    elif plant_type == 'Diesel':
        return 'Diesel'
    elif plant_type == 'Biomass_wood':
        return 'Woodchip'
    elif plant_type == 'Gas':
        return 'Gas'
    elif plant_type == 'Nuclear':
        return 'Uranium'
    elif plant_type == 'Coal':
        return 'Coal'
    elif plant_type == 'Solar':
        return None
    elif plant_type == 'OCGT':
        return 'Gas'
    elif plant_type == 'Recip_diesel':
        return 'Diesel'
    elif plant_type == 'Gas oil':
        return 'Diesel'
    elif plant_type == 'EfW' and construction_year <= 2000:
        return 'Waste_pre_2000'
    elif plant_type == 'EfW' and construction_year > 2000:
        return 'Waste_pre_2000'
    elif plant_type == 'Pumped storage':
        return None
    elif plant_type == 'Onshore':
        return None
    elif plant_type == 'Offshore':
        return None
    elif plant_type == 'Wind':
        return None
    elif plant_type == 'PV':
        return None
    elif plant_type == 'Pumped_storage':
        return None
    elif plant_type == 'Hydro':
        return None
    elif plant_type == 'Hydro_Store':
        return None
    else:
        raise ValueError('No fuel data for {}'.format(plant_type))
