diff --git a/data_adapter/preprocessing.py b/data_adapter/preprocessing.py
index 208c00f..67e27a3 100644
--- a/data_adapter/preprocessing.py
+++ b/data_adapter/preprocessing.py
@@ -117,7 +117,8 @@ def get_process(self, process: str) -> Process:
                             f"Foreign key for process '{process}' points to subject '{foreign_key.process}' "
                             "which is not unique.",
                         )
-                    foreign_df = self.__get_df_from_artifact(artifacts[0], foreign_key.process, foreign_key.parameter)[0]
+                    foreign_df, foreign_units = self.__get_df_from_artifact(artifacts[0], foreign_key.process, foreign_key.parameter)
+                    units[fk_column] = foreign_units[getattr(foreign_key, "parameter")]
                     foreign_df = foreign_df.rename({foreign_key.parameter: fk_column}, axis=1)
                     if artifacts[0].datatype == collection.DataType.Scalar:
                         scalar_dfs.append(foreign_df)
@@ -252,6 +253,8 @@ def convert_series(series: list[float], factor: float) -> list[float]:
                 continue
             if field["name"] not in df.columns:
                 continue
+            if isinstance(df[field["name"]].iloc[-1], str):
+                continue
             df_units[field["name"]] = field["unit"]
             conversion_factor = None
             for unit in self.units:
diff --git a/data_adapter/unit_conversion.py b/data_adapter/unit_conversion.py
index f2c24ee..fdd9ac6 100644
--- a/data_adapter/unit_conversion.py
+++ b/data_adapter/unit_conversion.py
@@ -46,6 +46,8 @@ def define_energy_model_units():
     scaled_unit("ktCO2eq", "tCO2eq", 1e3)
     scaled_unit("MtCO2eq", "ktCO2eq", 1e3)
     scaled_unit("GtCO2eq", "MtCO2eq", 1e3)
+    scaled_unit("Mt CO2-eq.", "ktCO2eq", 1e3)
+    scaled_unit("GtCO2eq", "Mt CO2-eq.", 1e3)
 
     scaled_unit("kEUR", "EUR", 1e3)
     scaled_unit("MEUR", "kEUR", 1e3)
@@ -68,6 +70,7 @@ def define_energy_model_units():
 
     scaled_unit("PJ", "J", 1e15)
     scaled_unit("kWh", "PJ", 3.6e-9)
+    scaled_unit("MWh", "PJ", 3.6e-6)
 
     NamedComposedUnit("Wh", unit("W") * unit("h"))
     NamedComposedUnit("kWh", unit("kW") * unit("h"))
@@ -100,6 +103,7 @@ def define_energy_model_units():
     NamedComposedUnit("MWh/MW", unit("MWh") / unit("MW"))
     NamedComposedUnit("MWh/t", unit("MWh") / unit("t"))
     NamedComposedUnit("MWh/kt", unit("MWh") / unit("kt"))
+    NamedComposedUnit("MWh/Mt", unit("MWh") / unit("Mt"))
     NamedComposedUnit("MWh/k_units", unit("MWh") / unit("k_units"))
     NamedComposedUnit("MWh/M_units", unit("MWh") / unit("M_units"))
     NamedComposedUnit("MWh/G_units", unit("MWh") / unit("G_units"))
@@ -166,6 +170,8 @@ def define_energy_model_units():
     NamedComposedUnit("M€/Million units", unit("MEUR") / unit("M_units"))
     NamedComposedUnit("MEUR/PJ", unit("MEUR") / unit("PJ"))
     NamedComposedUnit("M€/PJ", unit("MEUR") / unit("PJ"))
+    NamedComposedUnit("MEUR/Mt", unit("MEUR") / unit("Mt"))
+    NamedComposedUnit("M€/Mt", unit("MEUR") / unit("Mt"))
 
     NamedComposedUnit("kWh/100km", unit("kWh") / unit("100km"))
     NamedComposedUnit("MWh/100km", unit("MWh") / unit("100km"))
@@ -205,6 +211,7 @@ def define_energy_model_units():
     NamedComposedUnit("Kt/PJ", unit("kt") / unit("PJ"))
     NamedComposedUnit("kt/PJ", unit("kt") / unit("PJ"))
     NamedComposedUnit("Mt/PJ", unit("Mt") / unit("PJ"))
+    NamedComposedUnit("Mt/MWh", unit("Mt") / unit("MWh"))
 
     NamedComposedUnit("PJ/Million units", unit("PJ") / unit("M_units"))
     NamedComposedUnit("PJ/M_units", unit("PJ") / unit("M_units"))